Rich Harden just became a lot more attractive. He's still a big-time injury risk, but he's exactly the type of player you do extend a vesting option to, since his accrual of time on the field is almost certain to benefit the team, unlike that of, say, Alex Cora.
Gregg should draw some interest, as his strikeout rate is good, his walk rate so-so, and his flyball rate extreme.
3:43pm: As Sam pointed out in the comments, Harden is a Type-B free agent so this might make him less attractive if the Cubs have some inside info on his health. Then again, he could get $10-12 million guaranteed in arbitration regardless of how much he pitches in 2010 so maybe Chicago simply wasn't willing to take that risk.