They cut him because he was demanding a raise, not because of his ability. He's really, really good. The interesting thing about him is that it took him a long time to establish his foothold in the league. He's always been a freak athlete--truly a freak, even by NFL standards--but his play hasn't always reflected that.
I could see some teams maybe thinking that in their system he would be more like the player he was with the Dolphins, and less like the player he was in Philadelphia. Part of the reason why I thought he was a good fit here was because the Pats ask their linemen to get out and block in space a lot on screens and stuff, which would've showcased his athleticism.
Unfortunately, I think he's a great fit for the Broncos, too. For all the things he sucks at, Kubiak is an OL expert, and he's always valued athletic guards, even if they were undersized. Mathis is pretty much the perfect interior lineman for him, I think he'll do great there. Bummer.