> I plan on getting one in the next month or so.
> For the purposes of MAME, is there any reason to pony up the extra $100 for the
> additional L3 cache and hyper-threading of the i7?
> Also, any thoughts on the the built-in graphics capabilities?
I had access to an i7-820QM CPU (mobile quad-core @ 1.73ghz base clock, with turbo boost @ 3.02ghz) soon after the line was first released. From my experience with MAME, hyper-threading added nothing and in fact may have been one of the reasons most "challenging" MAME games actually ran slower than on my older 2.66ghz c2d (and there was no way to turn it off in the BIOS or otherwise). Note that this was in the face of all the marketing hype about the i7, with benchmarks demonstrating the proc's vastly superior speed over the c2d in just about every real-world case *other* than emulation.
For a variety of reasons, Sandy Bridge may deliver far different results under emulation tests than what you've been reading would have you believe. Also, any more cores beyond two might actually have a detrimental effect on emulation speed; so perhaps a dual-core i5 would be better in these cases.
Needless to say, until I see test results I will remain highly skeptical of Sandy Bridge and MAME, or any other emulator for that matter. That's not to say the platform isn't great for other non-emulation reasons, though!