Although Sherman (and Mike Martz in the Rams game) could be criticized for not going for it, you have to lok at the big picture, especially in Martz's case. Playing for a tie in a playoff game is going to happen more often than risking the win. If you had a QB who'd tossed three interceptions, are you going to take that chance and lose the game? I might have taken a few shots at a first down rather than the end zone, but I can't fault him. If either pass were to have been picked off, we'd all be saying "why the hell did he go for it instead of taking the easy tie?"
There was more to the Packers loss than that, or the Brett Favre ill-advised heave. They could have gotten a touchdown earlier instead of getting stopped on 4th and goal from the 1. They could have stopped McNabb's 4th and 26 pass to Mitchell for a game-saving first down. They could have kept McNabb from setting a new playoff record for QB rushing yards.
I've never been one to hang an entire game on one play, excpet in rare instances. The Packers did (or didn't do) plenty to keep Philly in it. Philly isn't a high-powered offense per se, but like Tennessee, you can't let them hang in there...they'll find a way to win.