White Sox about to deal Garland to Astros

The White Sox are making another pitching move today.  Looks like they are set to deal Garland to the Astros for Willy Taveras, Taylor Buchholz, and now it looks like Jason Hirsh is likely to join the deal, too.  I'm not as up to speed on National League prospects as I am with the American League; but that seems like too much for the White Sox to give up for Garland.  In my opinion, Garland is over payed and isn't anything special.

Thoughts from others who know a lot more about the Astros prospects then me?