Yeah it's a pretty nice piece of glass. It's pretty heavy though, makes the 70-200 VR seem like a toy!
I wan't really considering one, but saw one in mint condition going for a song on Ebay.

The only thing I don't like about it is that the AF is hit and miss when using a TC17EII (modified so the lens will mount). Annoying, because it's very sharp even with the TC! I just ordered a Sigma 1.4x so we'll see how that goes.
You're welcome to play with mine if you're at the T&T at WSID on the weekend.