thanks for sharing your GTS 250 story. I could not tell by the chart above that a GTS 250 with half the overall performance level of a GTX 470 would be a lesser card. I was really struggling with that one.
Nice....at least you have a decent hand at sarcasm!
Not that I'm interested in starting a flame war here, I wanted to share from my experience the difference I noticed. It was kinda meant for the OP, in case I wasn't clear earlier.
what brings me to my conclusion? those would be facts by various reviews rather then personal stories of fan boys.
....which we're just supposed to assume without any reference to, right? Would have helped if you place some reliance on citations backing your reasoning making it more plausible rather than one-liners which don't throw much light on 'why' you think so.
Back to the OP:
'IMHO', the performance of the 470 is better than the 275.....worth the upgrade i would say. The best way to figure that out would be to try some games and compare the difference from your previous experience with the 275. I'm gonna say that with tessellation and DX11, the 20-30% is a worthy difference.