I've always had mixed feelings about the Glass signing...
If you're going to carry a marginal player on the team just for toughness, you would think he would actually be tough. Say what you will about the need for a tough guy in today's NHL, Glass is just not that intimidating. He won't intimidate like a Colton Orr; he doesn't play an effective checking role like a Brandon Prust; nor does he provide energy like a Derek Dorsett. Glass just doesn't bring much to the table.
That said, the Ranger team without Glass is extremely soft. It may not show up directly on the scoring summary, but having someone on the team you know has everyone's back might lend the other players to play with a little more grit. Although I can't quantify it on the stat sheet, I believe that might be more valuable than replacing Glass with a Jesper Fast or Chris Mueller as the last forward on the roster. For now, Glass is the best we have in that regard.
The problem is that given his marginal talents, you probably could've filled that role just as well with a scrappy AHLer instead of singing Glass to a 3 year contract.