Smith is OK, but I agree with BAGF32 that he'd be better at RT than LT. BTW, wasn't he originally drafted as a RT? Not sure on that.
Faneca is gone - no doubt. Will be very hard to replace.
Mahan is OK.
Simmons needs to be on the first bus out of town after this season. A BIG mistake giving him the money that, in retrospect, Faneca should have gotten.
Colon is just a rookie, so I'm not ready to throw him under the bus just yet.
Still though, the OL must be the primary focus in the offseason, both in the draft and in FA if anything is out there worth bringing in.