First let me point out that I have never had any performance issues with my GTX 295. I run 1600x900 resolution and it's never had any issues with running maxed settings on any game I've played.
That said, I've pre-ordered Dragon Age II which supports Directx 11. Performance wise it seems like upgrading it to a Dirextx 11 card would be a lateral upgrade. Would upgrading it solely for directx 11 be worth it?
I'm currently looking at the GTX 480, and 570, which Tom's hardware has on the same tier as the 295.
I guess what would be ideal would be to see the game running both in DX10 and DX11. failing that as a posibility i would say that just for DX11, No its not worth it. thats just my personal opinion though.