I'll say what I said last year. Don't get me wrong, Harbaugh is a damn good coach and he'll probably have success where ever he winds up at next.
The difference between a good coach and a great coach is the ability to change the message and keep your team motivated. We always hear about his different mantras throughout the season, but I think the message is getting dull over the years and isn't translating with the vets on the team. As much as I hate the Patriots and The hoodie, he's a great coach who has always managed to motivate his players at all levels despite his longevity.
If you look at the draft history since he got here, we've drafted 5 pro bowlers, 2 of which didn't make it as a Raven, and 2 more in Flacco and Rice drafted the first year he got here.(Another fun fact, since the team came to Baltimore, we had 21 first round picks, 14 of which were selected before 2008. Of those 14, 10 made it to the pro bowl, since Harbaugh arrived out of the 7 picks we've had only 2 make it to the pro bowl, Flacco and Mosely) We all try and give him slack for lacking playmakers, but I have to wonder how much he is involved in the draft and how much of that is also his fault.
He won the super bowl 4 years after joining the team with a roster of talent which was built mostly before he got here. Since then the roster has been overhauled and he's had his guys in here we're 26-28. As much as he's done for the team I think it's time to move in another direction.