I replaced some on my own as well and, as stated above, I also feel the sensitivity is a bit off.
Don't get me wrong, Mario 64, Paper Mario and all that work perfectly fine, but for shooters it'll take a lot of time to get used to.
Maybe they're too 'new' and need to be 'worn' to be like how they used to feel.
Still, great buy, and getting them replaced wasn't all that hard either.