There are many (well, at least some...) good managers out there.
Mine was very helpful in letting me manage my exit (I gave him plenty of warning). I left in January so I could put some more money into the 401(k) and have the company fund their share of my HSA and other things. The big deal was splitting cashing in my options between the December and January (two different tax years). That was worth significant tax savings to me.
Finally, at my last review, I pointed out that I really had no use for the RSAs they were going to award me (they wouldn't vest), so please give them others members of the team. They did.