I helped a friend transition from an old XP laptop to two new Win7 laptops. He bought Office 20-whatever. I didn't open the shrink-wrap. I put LibreOffice on and told him to try it for a few days. I also pulled up his old version of Excel on his old computer, showed him a screenshot of Excel 20-whatever, and then opened the LibreOffice counterpart on his new one.
After a week, I've heard nothing about LibreOffice, but he doesn't like Win7 at all. I would've put Ubuntu on, except for two reasons: 1. He runs QuickBooks, and I was not in the mood to try to get that to play nicely under wine or some other hacky route. 2. Even though I run 10.04 LTS, I've seen Unity and absolutely don't like the direction they're going. Had they stuck with the interface in 10.04, I probably would've at least given QuickBooks under wine some thought.
This friend is not particularly computer-savvy. He runs an HVAC business. He doesn't want latest and greatest. He wants something familiar, and he wants it to just work. I think the open source community in general, and Ubuntu in particular, missed a golden opportunity when Win7 hit. If your product matches what the user was already using more closely than the next version of what they were using, you should be pushing that. Hard.
I have contact with lots of small business owners. If I suggested to them an OS that was free, looked and acted like their existing 2000/XP OS, and still ran their office suite (or a free 90% look-alike), and still ran their accounting/bookkeeping software of choice, they'd be all over it.