Down the years there have been many innovations in pad material. Some have been more successful than others, and in recent years there's been some development in synthetic pads.
But people seem to like the feel of leather pads, particularly on saxes, even though the choices have been rather limited.
Traditionally, cow hide has been the commonest type of leather used - but white goatskin (or kid) has been a popular option (and one that looks particularly good on clarinets) for several centuries.
There are subtle differences between the two skins, but none that really make an effective difference. Kid tends to be softer, which allows for a greater thickness of hide to be used - and this should increase resistance to wear...but then that may be offset by its comparatively poor resistance to wear when compared with cow hide.

And now there's kangaroo skin.

Various claims are made for the properties of kangaroo skin - and the one that really counts is its comparative strength, a property I was very keen to test.
And it was easy enough to test - the skin of a pad was taken off and generally tugged, bitten, and torn to see how well it stood up to attack.
I say torn - I couldn't actually tear the skin. Compare this with standard pad leather which tears quite readily. Even trying to pull it apart in my teeth had no effect - whereas the leather would always break.
Both samples were of the approximate same thickness, which means that the kangaroo leather is very significantly stronger than standard cow leather.

Another claim made is that kangaroo skin is less prone to sticking.
I'm somewhat sceptical of this claim because sticky pads aren't so much about what the pads are made of but rather what gets on them (your saliva, and various fats and sugars).
However, new pads are often sticky due to the various treatments necessary to prepare the leather - and the kangaroo pads exhibited none of the usual stickiness. Only time will tell if this remains to be the case once that pads have seen some hard use, but I believe it's a promising start.
I noted the kangaroo skin is quite slippery when wet, far more so than ordinary leather - and this may or may not be a problem once the pads have been in use a while.

There's an issue of porosity. Whether it's due to the treatment that plain leather receives, or the grain structure of kangaroo skin, it appears that these pads let rather more air through that ordinary leather pads.
I've been asked if I feel this is a significant issue - and I don't feel it is. You'd need significant air pressure to blow air through a pad whilst in situ - and if you could achieve such pressure in the bore of a horn you'd be beaten by keys normally sprung closed opening under the same pressure, not to mention lifting of the Auxiliary F and B keys.
There is some concern with regard to the ingress of moisture - but then this applies to plain leather pads to. All leathers will absorb moisture, which is why some pads are fitted with a polythene disc behind the skin to protect the felt core, along with treatments to the skin itself to make it more resistant to moisture.
Only time will tell if this is an important issue. I tend to feel that it will only really affect the pads that usually suffer anyway (such as the palm key pads and the low Eb) - so it's no change there.

It's worth mentioning at this point that the 'holy grail' of everlasting pads isn't perhaps all it's cracked up to be.
I often only see horns in for repair when they've stopped dead - usually because a pad's gone. In all the time that the horn is working, the action is slowly wearing. Assuming the pads never failed, I can see that the only time a horn would come into the workshop would be when the action failed...and by that time it would be a very significant failure, and a very costly repair - assuming you haven't been having regular services (and I know just how few of you book an annual service, whether the horn appears to need it or not!). Bear in mind too that if you have the action worked on, you often need to replace pads anyway (as the seating position may change), so you're back to square one.

The pads I tested were Steve Goodson's brand, finished in stained black skin and fitted with Noyek reflectors. This particular set cost around £70 by the time postage and duty had been taken into account. The pads are well made, comprising a stiff card back, a woven felt core and the kangaroo skin. There's no waterproofing polythene disc under the skin.
There's no particular advantage to choosing a coloured skin other than it has a cosmetic effect - and the combination of black hide and gold plated reflectors along with the gold lacquer of a horn is quite impressive!
The reflectors too were well made, and the finish was good. Gold plate should be ideal due to it being inert - and therefore corrosion resistant...but this rather depends on how well it stays on.
The theory behind the unusual scalloped design of the Noyeks is that the angular surfaces distribute the sound waves in a more widely spread pattern - thus (hopefully) giving more volume and more response.
The set as supplied contained only one significant error, the low B in the set was 44mm, the actual cup size is 42. A few other pads could have benefited from an extra half a millimetre in diameter just to make them slightly more snug in the cups.

Fitting the pads was easy - and the extra stiffness meant that there was less levelling to be done during the seating process. This is an advantage in that it saves time and doesn't stress the leather so much. The black finish on the pads made it slightly more difficult to rely on visual cues when adjusting the seat. Nothing a brighter spotlamp couldn't fix!

The finished horn exhibited less percussiveness on the action as the pads met the tone holes. You can of course achieve this with a softer felt core, but a harder pad tends to retain its seat better over a wider range of environments.

Compared with my own 62, the overhauled horn had slightly more cut in the upper harmonics overall. There was also an increase in the sense of attack to each note.
Whilst this was noticeable on the extreme lower and upper notes, it wasn't quite so effective on the mid-range - and my feeling was that the reflector's effect was akin to turning up the treble on a radio.
This can work - provided you have a full enough sound to start with, but it could have an adverse effect on a horn that doesn't have much body to the tone, or is already quite bright.
I didn't notice any change in the tuning or the focus.

The effect was more noticeable using my testbench Rousseau mouthpiece. This equates to a medium-bright piece with lots of mid-range. When this was swapped for the gigging piece, a Dukoff D8, the power and drive of the piece all but overwhelmed any slight changes in tone, though the extra cut up top was in evidence...perhaps too much so.

That there is a difference is undeniable - but what must be borne in mind is that similar - and greater - changes in tone may be brought about through less permanent options, such as a change of mouthpiece or an aftermarket crook.
Once you've had a repad, you're stuck with it - at least until you feel inclined to shell out again for a new set of pads.

I was suitably impressed with the kangaroo skin - so much so that I believe its a significant advance in pad technology, provided it can prove itself in the long term.
There are a few issues to contend with - that of availability and price for a start - and then there's the ethical issue.
Leather is a by-product of the beef industry, and as such the animals are farmed and the practice of slaughter is highly regulated.
Kangaroos are wild animals, and although considered vermin to some degree in their homeland I'm none too sure as to how or whether the process of slaughter is regulated. It's something I shall be looking into.

As for the Noyeks, I feel it's difficult to generalise the effect they have. I can certainly say that they'll give a YAS62 a bit more edge, but what they'll do to a different horn isn't possible to say without experience. I think it likely that they'll increase the punch and edginess, but this may not be an entirely good thing in some cases.
Thankfully they've been around a while, so there should be a wealth of personal experience to draw from in the sax playing community if you're considering them for your own horn.
Funnily enough, they may have rather more potential when used individually to adjust particular notes - perhaps livening up a lacklustre top C for example.
I should mention that the roo pads are available with a wide range of reflector options, including standard metal domed and plastic - and are available from MusicMedic.