He wouldn't be bad to have. I still question whether he'd actually crack a meaningful rotation: I still think if House is going to play, House is going to play "point guard" (even if Daniels or someone else brings the ball up the court). The real question then is whether Arroyo can supplant with his play making what House does shooting the ball. Honestly, I'm not sure he does that. Two years ago when Rondo had yet to prove he can play more than 25 mpg, Arroyo would've been really useful. But now that Rondo will play 38-40 mpg in games that matter, I think we can get by with the House/Daniels duo for 8-10 mpg. Especially when you consider the havoc Paul Pierce could unleash on opposing defenses if he's on the court with House, Allen, KG, and Sheed. There'd be no way to double him and he could destroy teams off the dribble.
Still, Arroyo would be a nice luxury to have. If Rondo went down for a few weeks, he'd be a lot of help. I'm just not sure that if everyone is healthy he'll actually play.