Well, 2600, 2600S, or 2600K and also compared to which current i7? Also keep in mind, if you buy a current i7, the 1156 and 1366 sockets will soon be obsolete already. So if you are planing to build an i7 system with 1156 or 1366 socket... you will have very limited or no future upgrades to your board.
Also the new sandybridge 2600's will have newer and better integrated graphics and most of the current motherboard controller funtions built in. Also, all 2600 models are 95W or less so far.
I asked myself these same questions... and I think I am going to wait for the new 1155 socket boards and CPU's to start selling for a few months before I decide... because if 1156 and 1366 are dead... I will be in a bad situation... just like I finally decided to nix all me Pentium 4's and Pentium D machines for the latest Core 2 chips... then they sharply discontinued the LGA775 platform... so far I am kind of skipping the i3,5,7 deal until they get the new sockets and boards worked out.
As for performance... just compare the i3-530 to the core 2 duo e7500... other than 1MB more cache and a few small details changed, that is why I am skipping this generation. They want you to keep buying the same crap in a new box. So I think waiting for the 2600 is better because the 1156 and 1366 are going away like the 775.