Leslie Frazier might be a second-rate coach; jury is still out on him since his two primary problems were a) being too conservative, and b) Christian Ponder. He had to go, no question, but I'm not convinced he can't be a successful head coach in the NFL if he learns from his failure with the Vikings. See: Bill Belichick.
When the whole coaching carousel kicked off, my preferences were Whisenhunt, followed by Zimmer. So, I'm pleased that the Vikings hired one of the sane candidates. And the fact that they didn't hire Jim Caldwell AND get the benefit of playing against a Caldwell-coached team twice a year, is a bonus.