I purchased the Poweriser Advanced and a Classic set both from XPhub.com I ased for this upgrade kit and so far mine have been working well for me.
It most likely has been smooth and quiet simply because I am not a very heavy person I only weigh like 95 pounds without stilts on,
I did notice though I got a friend of mine the heavy spring he weighs about 200 pounds and I upgraded my classic pair with the new 90120 springs and this kit and sold them to him and so far he has a little click sound a very minor movement from side to side at the hoof joint but it is so little it seems to only need one extra brass washer which I added and all was great on his pair so far.
Myself I made a bushing for my spare set by getting a nylon black bushing from my local Ace hardware store about 37 cents us dollars each and drilled the inside hole a little bigger to let the metal slide rings fit through it and tried it out for a week and works great as a replacement part.
This bushing is the same thing that
www.Air-trekker.com has on the site for a replacement part and is found in my new M115 frame I just got.
I still like my Advanced better simply because of the (tiny) leg issue I have but still working on Mods to make Air-trekker fit my legs better like the foam/tape idea it works well too.