Really? I think with the talent level they have he has done a decent job, and they are headed in the right direction. He's not a great x/o guy, but neither are a lot of head coaches in the NFL. NY fans are typically delusional. I'm sure after the Giants won, Jets fans are even more irritated. I look at Carolina. They could have run Fox out of town, but didn't and now its paying off.
I think your point about talent may be the reason Mangini is fired. Last year they didn't have the talent, then they went out and spent a shitload on top level players. However, since the Titans game, the Jets have gone from 8-3 - 9-7. Today Mangini made several very poor coaching decision that might have cost them a playoff spot. If NE can win the east with 14 players on ir and Brady out, the Jets will fire Mangini and go after Cowher, imo.
One thing Mangini has done a good job at is drafting players (aside from Gholston) who I liked in college, btw.
Lastly, your point about NY fans is a good ones. Thats the problem with Mangini, he has been making bonehead mistakes, and the fans are going crazy.