You can find my thoughts, along with those of a few other people here:
http://www.bikeforums.net/showthread.php?t=450604
The only complaint I've had is with the brakes, and I've fixed that to my satisfaction recently (see the more braking power thread).
I'd say $400 is a great price if all the components are in good shape. Make sure you can shift well through all the gears (STI shifters are expensive to replace if they're broken).
Ask if it's been used for cyclocross racing -- that's not necessarily a dealer breaker (I use mine for that and it's still in great shape), but it's rougher treatment than most bikes get. If it has, take a close look at everything to make sure nothing's broken. Make sure it shifts cleanly through the full range of gears. If it doesn't see if you can have a mechanic look at it before the sale is final to make sure it's nothing major.