By the numbers:

2005 - QB Rating 75.9, 235 yards/game, 24 TDs and 17 INTs
2006 - QB Rating 77.0, 202 yards/game, 24 TDs and 18 INTs
2008 (pace) - QB Rating 79.5, 198 yards/game, 26 TDs, 18 INTs

In short, my answer would be.. not really. He has consistantly been a slightly above average QB over the past three years. There is moderate credence to the idea that aside from the numbers above, he's a "gamer", a "clutch" QB, whatever you want to call it. Consider that his QB Rating in the 1st, 2nd and 3rd quarter over his career is a combined 72.3 - a number that jumps to 79.5 in the 4th quarter (additionally, 21 of his 67 career TD passes have come in the final 15.)

So, has he been making huge strides? No. But he's played well enough that, surrounded by a decent supporting cast, I'm convinced he can take us to a Super Bowl.