So my big quandry is whether I should use the excuse to migrate the blog, or to end it.
And by "end it" I don't mean "stop writing." I've had a number of very nice offers to join other group blogs in the past. Maybe this is the right opportunity to leave the solo path and join one of the group thingies. I'm certainly not up to writing at the everyday pace any more regardless.
On the other hand I would hate to lose the feeling of independence that comes with one's own blog. I can publish what I like here without regard to any other standard than my own. And I need never worry that someone else may override that decision either. That's not nothing.
Anyway, if the half dozen remaining readers of this thing have an opinion, I'd love to hear it. Otherwise... well I'll try to let you know before things go black here.

For what it's worth, Night Writer moved from Powerblogs recently; he might be able to give you some insights. He's in Spain now but should be coming back to the States soon.
I bagged Powerblogs back in June, mainly because the support had become non-existent (not that I required a lot) and I wanted to refresh the look. I hadn't heard anything about PB going away, but it was clear that Chris wasn't paying a lot of attention to the tool or adding new services, templates or capabilities. I went to WordPress because it seems to be the dominant host now and has a lot of flexibility thanks to the large numbers of people designing plug-ins and widgets. Unfortunately, since PB is kind of an odd duck, there wasn't an easy way to transfer all my archives but Kevin Ecker spent a few hours at my place one Saturday working me through the process (I'm nearly illiterate in blog mechanics). He moved my existing content to Movable Type (using the PB MT tool) and then from MT into WP and everything - even the hyperlinks - came through in good shape.
As for your original question, I'd vote for keeping a solo blog for my own selfish reasons. One of the things about the blogs I like is the "voice" of the writer and the anticipation I have when clicking on that link - especially if I'm in the mood for a particular style or type of insight. I find it more difficult to do that with a group blog, especially those who don't identify the writer until the end of the post. Not that there isn't good stuff on a group blog, but I guess it's a bit like preferring a boutique store to a big box retailer.