For fear of jinxing McGowan one way or the other I will abstain from responding to the question. Here are some stats that might make the situation a bit clearer:

          Strikes  Balls   P/PA   GSc  (2007 P/PA)  P/PA diff.
5- 3  CLE    57      46    4.12    34    3.96          0.16   sigh
5-12  TB     58      37    4.13    44    3.80          0.33
5-18  PHI    46      40    4.10    39    3.85          0.25
5-23  BAL    54      33    3.34    45    3.74         -0.40
5-28  NYY!   78      39    3.90    67    3.88          0.02   look out world!
6- 2  CHW    59      44    3.43    55    3.72         -0.29
6- 8  LA     56      25    3.24    65    3.61         -0.37
6-13  SF     53      43    3.56    52    3.68         -0.12   no Barry

The at-bats are getting shorter, and he's throwing fewer balls. This reinforces the declining walk rate. It sure looks like McGowan is pitching more aggressively and with better command.

The catch is that this trend coincides with McG facing increasingly hack-happy offenses. In his first five starts, he drew three AL East teams, the dreaded Indians and the sleeping-giant Phillies. In his three most recent starts, he faced two NL West contact machines and their spiritual cousin on the South Side. So what degree of McG's increased efficiency can be attributed to him getting settled in or improving, and what degree should be blamed on bad competition? Hard to say, especially considering the huge role dumb luck tends to play in eight-game samples.

Looking specifically at the "bad" start against the Phillies, he had a no hitter through four innings (1 W, I believe) and then couldn't get out of the fifth.  That speaks to McGowan's composure more than anything the Phillies did.  He walked the pitcher in that inning and had a couple of "less than sharply hit" grounders make it to the outfield grass.  I was pretty encouraged by that start because I didn't think 5th Innings like that one would persist if he was given a decent run of starts.  Au contraire, it seems every time a runner gets to third, he starts striking out batters instead of walking them.

On the flip side from the stats... I was at his start against NY and was watching him warm up in the pen. He seemed to be doing what he wanted with the ball at will, something I hadn't seen from him in earlier starts (I always try to get to the game to watch the pitcher warm as I regularly get tickets in that section).

I think even his bad outing this year were positive and his confidence has grown as he's accepted that he's here and not going to get the hook or be bounced to the pen after minor struggles. Why they couldn't get this out of this last year, I'm not exactly sure.