It can sometimes mean that.
I made the switch just recently, went from a hd4850 to a 560ti. I got my 4850 because at the time they represented a pretty good bang per buck. But I always kinda liked Nvidia, having used them ever since the demise of 3dfx, so I was glad to come back to the green team.
Unfortunately, it seems nvidia's the drivers are not without their problems too. There's an issue that cropped up since the 28X.XX drivers, for more info see here:
http://forums.nvidia.com/index.php?showtopic=65161
Its supposedly partially fixed in the new drivers, and will be fully resolved in the first set to come out after Christmas. Oddly, it only affects me when I'm browsing the web. It's not a huge problem, and it doesn't affect everyone, but it is aggravating.