I'm going to throw in my two cents...
On the surface, Dallas is primed to have a HUGE offense now. They fortified the offensive line, and now signed T.O. Last year Terry Glenn had a big season, facing double coverages from opponents' top cornerbacks/safeties. All of the defensive attention will be placed on T.O. now, which means HUGE opening for Glenn. Not to mention Dallas faced eight-man fronts rather often last year, meaning little to no room for Julius Jones. You can't drop a safety into the box when T.O./T.G. are on the field at all times and not pay for it, which means big running lanes, too. Plus, you can't afford any cornerback/safety help on Jason Witten now, either. This could be QUITE an offensive show.
However.....
T.O. is a cancer that ruins teams. Yes, Dallas is used to these players and yes, Bill Parcells is, too. However, T.O. will be T.O. and that's that. When Drew Bledsoe hangs in the pocket too long and gets sacked (which happens quite often), do you think T.O. is going to calmly walk back to the huddle and not say a word? Of course not. Do you think T.O. is going to take a sideline lecture from Parcells in stride? I don't.
Alls I can say is this signing has potential to take Dallas to the top. Luckily, the contract was built to allow for an easy release if he becomes a problem, and unlike Andy Reid, Parcells won't put up with any of that nonsense he pulled in Philly.