blazorthon :
For desktops: Games do take advantage of Hyper-Threading. It allows the i3s to smack the Pentiums and Celerons around in most DX11 games. Most games don't respond all to well to it on i7s (although this is changing rapidly) because the i7s have eight threads whereas most games scale well across only up to four. Again, this is quickly changing and we're up to at least half a dozen games that can take advantage of eight threads quite well.
It is still accurate to say AFAIK that 2nd and 3rd generation i5s are still more than enough for all current games, so an i7 is almost definitely not worth getting in a gaming system when it means that you can't afford a decent SSD.
For laptops: Going from a dual-core i5 to a dual-core i7 doesn't seem worth doing at all to me because they're both similarly clocked dual-core chips with plenty of cache, Turbo, and Hyper-Threading. A dual-core i5 is still a pretty quick CPU for gaming with the current generations and the sacrifice of an SSD is too great to go for a dual-core i7. Even a quad-core i7 is probably not worth getting at the sacrifice of an SSD.
Just a friendly reminder, the i7 I am refering to is a dual core, with two hyperthreads per core.
Also, I won't be playing any intensive games (probably just some Starcraft, Minecraft, and Half-Life 2, maybe some Portal 2) and am planning to carry it around a few days of the week.