While Deangelo Vickers would never be a worthy replacement for Michael Scott--nobody would be--he should be a decent character--funny and, at the very least, consistent. Deangelo is neither; he's bizarre, always changing, and just not funny. The end of the episode, Deangelo returning brain damaged, tells us that we don't have to care about him anymore and that he was never important. So why spend all this time with him? Yeah, it's Will Ferrell, but the writers did nothing good with him.
The departure of Michael does free up some options, and we got to see a larger variety of characters than we usually do. There was some Dwight, Ryan and Kelly, Jim and Pam, and almost everyone had a line here and there. But there's no substitute for a good plot, which is what the episode needed, and, of course, there was Deangelo.
Score: 7.4/10