The only thing stopping me upgrading at the moment is compatibility with older games. I play Grand Prix Legends a lot, which is a game from circa 1998 and has had numerous updates from the community to try and fix the relentless push by the GPU manufacturers to break older game support in new drivers and video cards.
That and I can't justify it because I'd need a new rig to support the thing. My Celeron 800 wouldn't cope.