As of now, very little benefit.
However, that said, more and more games are making use of multiple cores, it seems to be a fairly safe assumption that as games get more complex and demanding of the CPU, they will make use of HT.
Bad Company 2, GRID, UnReal Tournament III, L4D2 are 4 games I can currently think of that make use of HT by spreading the load over 8 cores (on an i7)
I recently read about a game (sorry, cant remember if it was one of my flight sims or a future release) that will use 1 core just for processing sound. Maybe in the future devs will structure games to offload certain intensive tasks to individual cores (ie: sound, physics, etc).
If its going to be a while before your next upgrade, an i7 CPU may be better in terms of future proofing your PC (you could use a single core to run your hacks!).
Also, I believe the i7 also has a larger memory bandwidth than the i5.
I think more than 6GB ram is excessive unless your going to use it to create a RAM drive to run certain disk-intensive apps/games from.