The migration process has been flawless and trivial. After the change nothing seemed to have changed except for some minor nits in the UI. I looked around for the labels feature but discovered that it is only available once you migrate to the new "layouts system", an easier way to desing your blog's look.
The switch to layouts scared me a bit because I was afraid of not being able to integrate the Statcounter code back again. But after verifying that the change was reversible, I tried it. I can confirm that the new customization page is much, much easier to use than before, although still too limited (direct HTML editing is not available yet). Oh, and I seized the oportunity to switch to a slightly different theme (yes, it was available before).
Aside from that there are some new nice features such as RSS feeds (weren't they there before?), a better archive navigation (see the right bar), integration with Google accounts and many other things I'm surely missing.
Summarizing: It has taken a long while for the Google people to upgrade Blogger's service, but the wait has been worth it. Now more than ever, I don't regret migrating from Livejournal to this site almost a year ago.