I kind of like Arroyo, and think the Pirates made a mistake cutting him loose. He's got excellent control, a live enough fastball, and a nice hook. 83-44, 3.80 lifetime in the bushes is not bad at all, and he showed well last season in a handful of relief appearances for the Red Sox. The fact that he walks very few batters is a big plus from a WHIP standpoint, in that while he's likely to have plenty of 6 IP, 4 ER types of outings, he won't murder your WHIP in those starts. Nice deep league or AL only stab.
As for Kim, he's history in Boston. He was on shaky ground after his late '03 meltdown, and his reaction to being demoted to Pawtucket was likely the finish. He'll be traded a.s.a.p. and I suspect the Sox don't care what they get in return.