Yup, those gamecube-style replacement thumbsticks feel very nice, but they play like garbage. They have a microcontroller that converts the potentiometer signals into what the n64 would expect from the original optical encoders. They're poorly programmed, and have pretty big range and lag issues. Depending on what game you're playing, it ranges from bad to unplayable.
You can actually reflash or replace the microcontroller to fix this, the code is available online. This will get you about the nicest N64 controller possible, and it won't wear out quickly like an original. If you're not up for all that hassle though, just the replacements as-is aren't worth it. Just look for original controllers in as good of shape as possible