Gaming performance with a discrete GPU does improve in line with the rest of what we've seen thus far from Ivy Bridge. It's definitely a step ahead of Sandy Bridge, but not enough to warrant an upgrade in most cases. If you haven't already made the jump to Sandy Bridge however, the upgrade will do you well.
AnandTech - The Intel Ivy Bridge (Core i7 3770K) Review
Definitely not worth an upgrade if you already have a Sandy Bridge.
Just my 5 cents though. Hope this helps!