He's had a couple of deep runs since 2003. I'm no Hellmuth fanboy, but credit where credit is due. The guy cashes in and wins a lot of live tournaments. From this we can infer that he probably isn't the worst tournament hold 'em player out there. Beyond that, who the heck knows. As for other games, it seems pretty clear. When the cash game regulars are willing to build games around him, you can be pretty sure that the consensus is that he, how do you say, "lacks edge" in those games.
http://www.cardplayer.com/tournaments/results/7083
25K WPT championship - 18
http://www.cardplayer.com/tournaments/results/3718
Heads up championship - 1
http://www.cardplayer.com/tournaments/results/2373
Foxwoods WPO - 3
http://www.cardplayer.com/tournaments/results/3744
Jack Binion's WPO - 8
Bunch of other wins and final tables in smaller events...