Thanks to MacSparky's post on upgrading to Squarespace 6 I made the plunge this week and did the upgrade myself. I was so daft about the announcement that I didn't even realize it was a manual upgrade, I just thought it would happen!
But the process was fairly painless. I had two questions that I emailed to support and in both cases they got back to me promptly and more importantly, got back to me with helpful information.
There is a learning curve insofar as it is different than version 5, but I think I've spent less than two hours on this and have managed to tweak some CSS, add in my typekit font, take off the 'share' button, and make some other changes I wanted. And, I actually like it more than my previous site after only a couple hours.
Kudos to the Squarespace folks for making it easy and dare I say, fun, to play around on my site.