This makes a lot of sense. Pursuing Hunter/Rowand upgrades the defense, but from an offensive perspective, they're probably comparable to Scott, but making $10-$15 million more.
Castillo clearly upgrades one of the Astros' current weaknesses (well, without Loretta) heading into 2008 from both an offensive and defensive perspective. In addition, it's been a while since the team has had a legitimate lead-off hitter in the .360 OBP range with a very low strikeout total.
If Rosenthal is accurate, I like this a lot.