Now I think of it, the upcoming release of XNA Studio Express is the first opportunity for the public to run the exact same code (well, almost, given that there’s an invisible runtime beneath your code, which is NOT the same) on a retail Xbox 360 and a PC. This means you can get a fairly accurate comparison of low-level capabilities of Xenos vs. your own PC GPU - it should be easy to devise test which stress only shader power, or only alphablending bandwidth, or only geometry througput, while taking the CPU out of the equation. These results would be useful for all PC developers planning to eventually target the 360. I vaguely remember something about the EULA for one of the previous .NET frameworks explicitly forbidding publishing benchmark results, but with the XNA Studio in open circulation and something like 10 milion 360s in the wild I don’t think such results could be kept under wraps.
It should also be possible to benchmark the CPU running MSIL, but that would only be of use if you’re actually planning to make your game in C#/XNA framework, which, while probably a reasonable plan for simpler XBLA titles, I don’t expect to become popular with full games.
Update:В Well, it seems the EULA for XNA expressly forbids disclosing benchmark results without Microsoft’s consent. You won’t see me doing this, I promise