It isn't like Justin Upton is some superstar defensive whiz. Over his career, he's been pretty much dead-center average.
He's probably going to cost one of the B's, and maybe another very good piece like Cecchini/ Doubront/ Lavarnway. If he can be had for cheap then awesome, let's do it. Otherwise, even if he adds .100 OPS to his stats and stays perfectly healthy over that time, I'm still not sure if he's worth it.
There are so many options available. Hamilton, BJ Upton, Bourn, Victorino, Cabrera, Swisher, Ross, Pagan, Hunter. Trade options like Choo, Willingham and plenty of others are out there.