The 90-series drivers are mostly pure crap. They force you to use .NET architecture, which drains resources and slows you down, even if you don't want it to. On top of that, they seem to be no better than their predecessors, which have a much smaller footprint.
Only problem is, some cards only take the 90-series (like I bet the Ge8000's require it, as it's probably the only driver recent enough for the newer cards)