Okay, seriously, here's my question to startup website developers. Is it wise for us to spend significant time trying to avoid using tables in our often-changing layouts, in the hope that a blind user may have a slightly less confusing experience? I'm not quite going to say YAGNI, but I will say I'm not convinced.

If you're serious about accessibility, good for you -- use VoiceOver or JAWS, truly check your site out. It's a lot more laudable a goal than having your HTML perfectly pass some XHTML validator. Otherwise, I think it's one of those things we can sensibly put on hold until after our B rounds.