Sox enter the second half of the season with a 3 game lead over the Yanks and a 6.5 game lead over the Devil Rays. If you look at what the standings 'should' look like, via pythagorean run expectancy,** the Sox and Yankees are overperforming by two games while the Devil Rays have been 'unlucky' to the tune of three games. In other words, in the world of statheads, the Sox 'should' have a 1.5 game lead on the Rays. Based on the Sox (actual) winning percentage of 0.614, you'd extrapolate out to a 99.5 win season, which would be damn good. For a slightly more historical take on where the Sox are going, this site offers a method of analysis that predicts 96 wins for the Sox, with a standard deviation of 5 games (if you follow the link you won't find that prediction, but following his formula that is what you get).
The Sox of '09 are looking remarkably like the post-season version of the '08 Sox . The starting pitching is good, anchored by Beckett with solid-and-sometimes-brilliance from Lester. Wakefield does what he always does, sometimes getting shelled, sometimes going 8 innings of 1 run ball. Penny has been more durable than expected, and Smoltz appears to be getting better. Buchholz has been waiting in the wings all season, and get his first ML start of the season tomorrow. So yes, the Sox currently have 6 starting pitchers on their roster (don't expect it to stay that way -- Buccholz probably gets sent down after his start, regardless of how he pitches).
The hitting goes through some frustrating spurts of non-production, but at the end of the day, the Sox are third in runs scored in the AL, so the lineup is doing its job. Papi has risen from the dead, SS is still an offensive hole, and Lowell can't stay on the field. I'd say this is the biggest area of concern for the team, because no one wants a redux of last years ALCS lineup, which had way too much of Mark Kotsay in it. The return of Jed Lowrie helps this out a little bit, as he can play third if Lowell can't go (or if Papi can't play, then Baldelli or Lowell work as DH), but Jed Lowrie is not carrying you through the playoffs (as we saw last year).
Anyway, I'm feeling pretty confident in this team's chances. Unless the Yankees get Halladay, I think the division will again come down to the Rays and the Sox -- the Yankees just don't have nearly enough pitching, either in their starting rotation or in the 'pen to effectively compete. The Sox have zero games remaining on the West Coast, while the Yanks have 13. Of the three teams, the Sox also play the easiest remaining schedule, with opponents of a 0.505 winning percentage (0.515 for the Yanks, 0.522 for the Rays). Even if they don't take the division, it is hard to see the Rangers or the White Sox or anyone else who's not from the AL East taking the wild card -- indeed, Baseball Prospectus puts the Sox chances of making the playoffs at 82%.
** Expected won-loss record based on runs scored and runs allowed, using this formula: RS^1.82/((RS^1.82)+(RA^1.82))