Have the Nats been using it a lot? Besides for Howard?
I feel like the shift is in vogue at the moment, though I have no real evidence to support that.
I believe I've seen it against hitters other than Howard, but can't recall specifics.
Last year, BP did an article on the shift, specifically focusing on Zimmerman and how exceptional he is at turning the DP as if a SS. Exceptional in that no other 3rd B is even close over the last 3 years. He's got maybe 7-8 vs. 1 or 2 for the next guy down.
On the down side, one time a player (Rollins?) ran right past Zimm at 2nd and cruised into the unguarded 3rd base.