While not everyone can migrate to the new version (large blogs should wait a little bit more), Blogger is feature-complete and doesn't have major bugs.
"The new version of Blogger is metaphorically bursting with features, from the big guns like drag-and-drop template editing and post labels (...), to little polishes like a better-designed Dashboard or that you no longer need to solve a word verification CAPTCHA to post a comment on your own blog."
Hopefully, the Blogger team (or what's left from Blogger) will also add basic features like: comment spam detection, no separate page for posting comments, photo management.
But for the moment I'm happy: if you change the title of a post, the URL remains the same. In case you've seen a 404 error here, this must have been the cause.