You know, I was all set to groan and point you at the thread on the $79 Nashbar CX frame, but then you mentioned the 105 components which made me do a double take and look at the spec for this bike. Doing so, I see that it's not the same frame as the $79 model that Nashbar sells. The fact that it's steel should have tipped me off, but I really had never paid very close attention to the other frame either.

Anyway, at 20% off this definitely seems like something worth taking a chance on. It would definitely work for commuting, and you could race it, though I expect it would be a bit heavy by racing standards.