[creedo]

Not an expert, but I think horndoc's right there. 6.1 with or without sense should be pretty fast and reliable. 6.5 (or at least 6.5 running with sense) has this memory leak that will make the phone slow and chuggy after a few hours, requiring 1 or more resets every day.

I have been really happy with mightyrom, I noticed a performance improvement right away and I wasn't getting SOD/errors/crash, at least not until I overclocked it.

But you won't need to OC if you use the thing for business and don't load it with a bunch of unneeded apps and overdone themes. In fact even the stock rom people are hating on is responsive and stable if you just keep it to 2-3 apps at once, including a non-intensive web browser (latest opera mini is awesome). At least that was my experience, I used it for a couple of months with no problems, it only started getting slow when I started adding a bunch of stuff to the phone, once I discovered the joy of cabs.