I didn't call them evil, but they certainly haven't been helpful to the open source community. Of course they're under no obligation to be and are currently doing a stellar job of supporting their product under linux.
But if one day nvidia decides there's no money in linux desktop drivers then there's no free alternative and we're all screwed (I've got a nvidia card too).
See Oracle's recent takeover of Sun for example - what's going to happen to OpenOffice or MySQL? Maybe they'll keep supporting them, maybe not. But it doesn't matter so much because they're open source and therefore forkable if someone wants to maintain them.