I tried them before Eliza came to live with us, so I only had Bach and Mozart at the time...
I didn't mind it, the problem was.. the cats loved it a little TOO MUCH... What I mean by that is, When they pee'd in it (or on it rather).. it makes this sound... well they LOVED that sound, so they would pee in there about 20x's a day (needless to say I didn't have to worry about them drinking enough water!), so it quickly didn't last a week with them!

Not to mention.. those things HURT to step on!!!

As for smell... it certainly didn't smell... but it wasn't economical for me, so back to regular litter we went, so that we wouldn't spend mega bucks a week on the fancy stuff that makes great sounds when you pee apparently!

But if you try it and like it, and it lasts a month or so (its supposed to last a month for one cat i think).. then GREAT! I had expected to get 2 weeks out of mine at least... but didn't make it a week, once they thought "ooh wow, REALLY cool stuff" lol.