[Arterion]

Sprint 6.1 Stock ROM is the fastest, IMO. MightyROM is really good. vin's ROMs are pretty good, but they deviate a little from the "stock experience" look and feel, which kinda turns me off to them. For me, it's a lot easier to add customizations than to take them away.

I the the bottom line is, you're not going to find anything much smoother than the newest MightyROM flavors.

It's kindof a given that Sense 2.1 is faster. We can quibble over WM 6.1 vs 6.5 -- 6.5 has better memory management -- but it's requirements are also a little more intensive. I personally find 6.1 is faster, but don't fool with it anymore because the UI graphics are so dated.