All in all, I really like it.
I like that there were 3 different types of thumbrests in the package. I didn't like that they came on a single strip of adhesive, requiring you to cut around the thumbrest to remove the one you want. But once removed from the strip, it was an easy install (just peel the backing from the adhesive and stick it where you want). I was worried that the adhesive wouldn't be strong enough to handle the pressure that might be exerted on it, but it holds perfectly. I think waiting 24 hours before playing after installing the thumbrest helped the adhesive to set properly (although the instructions say 8 hours is adequate). All in all, I really like it.