Copy protection sucks, at any rate.
I never had issues w/ Waves, but:
I've had problems w/ Focusrite plug-ins losing the authorization every 3 months, pretty much like Bit's issue w/ Waves. I have to request a new code every time, but, at least, we're in touch and I know they're working on it.
Cakewalk - Zeta unauthorized itself every month. But instead of asking me to re-authorize it, it gave me a stuck note - usually the most unbearable deafening sound you can imagine. Last time I had the headphones on and if I wasn't such a wuss and worked at normal levels, I could probably sue Cakewalk for permanent damage to my ears. Between you and me, I'd still prefer a pop up.
And then there's the IK libraries - just don't move them unless you have a bit of time to re-authorize and/or re-install.
I'm starting to like my iLok, man...