I've always used the web drivers for my gtx680 mac edition in my mac pro 4,1. The other day I installed some more ram and did a PRAM reset and the machine booted using the built-in OSX drivers (this is normal). I didn't catch it, but noticed over the next couple of days that my performance in Guild Wars 2 was much more fluid and maintained high framerates more easily. It wasn't until I was poking around in my control panel that I noticed the Web Drivers (latest version) weren't enabled. I switched back and forth from the Web Drivers to the built-in one and definitely see a big improvement with the built-in drivers. I've always heard that for most people the Nvidia web drivers provide better performance, so I'm a bit puzzled at what I'm seeing here.