Actually, the jury is kind of out on that one.

I say that because Fox might have brought the subject up due to a tweet I sent him this past weekend. On our guild's Sinestra trials (We finally got here last week. Yay!), I was doing some horrible dps compared to both the other shadow priest in the raid with similar gear and to my previous dps since I'd equipped a new piece. I'd also noticed that while I'd casted MB with orbs up, I wasn't getting the buff. I went entire egg burn phases with no Empowered Shadow buff, and that little bit of missing dps had cost us the attempt. I checked the logs and sure enough I'd missed with a MB here and there.

I capped my hit and all was right with the world for me again.

I've gotten mixed answers from various sources (shadowpriest.com, guildies, etc.) when I asked: "Does Empowered Shadow refresh on HIT or on CAST?" Typically speaking with most spells, you gain the benefit of a spell when it hits and not when it is merely cast. Then again, the benefits of our buff are supposed to be realized when an orb is consumed (on cast). All I can tell you is that capping hit worked for me, and I've not seen a very costly dip in Empowered Shadow since.

It would be nice if I could get a straight answer from a GM on this one.