One of the things I like about Upton's swing is that he generates tons of power but doesn't have a lot of "noise". Specifically, he doesn't get far away from a good swing plane. Here is an illustration of what I mean, just before Upton unloads his swing:
[caption id="attachment_2883" align="aligncenter" width="338" caption="Justin Upton swing plane"][/caption]
Lots of bat speed + consistent swing path = power AND consistency!