In my opinion, I agree with Shady and Aiastelmon...he was horrific last year, and better this year; he has been hitting a little more "productively," (i.e. more often than he did last year WHEN the player has the puck, as opposed to AFTER -- which was the case 95% of the time last year) and is doing a decent job blocking shots, BUT...
...he REALLY does a poor job offensively -- and I don't mean scoring goals or setting them up. I'm talking about doing his part to maintain possession of the puck in the O-zone, while on the forecheck. To me, that's the job of the bottom 6 -- to play with energy, and to be good forecheckers (in ADDITION to being good defenders when the puck is in the D-zone). SO, while Glass does a decent job at times laying out hits, he's not in my mind all that physical in terms of board play -- i.e. doing his part through his stick- and body-checks to either force loose pucks/turnovers in the D-zone, or in winning puck battles to sustain possession while on the forecheck in the O-zone.
That would be how I view him; he is an offensive BLACK HOLE (and again, I'm not talking point production, I'm talking about helping to maintain possession time in the O-zone when on the forecheck).
He in my mind is decently suited as being a part of a very physical 4th line, which is deployed RARELY, and in situations where the coach SPECIFICALLY wants a punishing, physical shift from that line. Pairing him with two very physical players, and sending them out when you, as the coach, want to send a "physical" message, is what he's most suited for, IMO.