Yes, it is certainly a terrific lens, Scott! I just added a Kirk replacement foot to mine:
http://photography-on-the.net/forum/showthread.php?t=1426176
(See page 2 of that thread)
That's one of the reasons I went to the zoo yesterday, to try out the new foot with my Wimberely sidekick...
My most recent acquisition is the new Canon 100-400 Mk II zoom. I've owned the original 100-400 for many years. I had the original one fine-tuned (serviced) by Canon Irvine and, frankly, I don't think the new one is any sharper. But, the IS on the new one is several stops better. And...