[Brian]

OmniFocus 1.6.0 and earlier aren't going to be happy about the new database format, but they'll just fail to read it. (Possibly crash trying to do so.)

I ran 1.6.1 on my home machine while testing v1.7 here at work for a couple of weeks specifically to try and flush out any issues. (10.5 at home, 10.6 at work.)

Thus far, my data hasn't suffered any ill effects, and I'm not expecting 1.7 -> 1.7.1 to be any different.