I guess in some ways it's supposed to be one of the more difficult SANS offerings since it's a 600-series, but that said I already had some experience looking at wireless captures, working with 802.1X, etc., so not getting at least a 90% on the exam is pretty lame, although I came close. I got my OWSP a while back so you'd figure I'd have some decent base to work off of, but I think it's my general lack of immediate interest in DECT and ZigBee that got the better of me.
I spent an entire quarter going through SEC-617 (OnDemand) but the work schedule didn't really permit me to keep my head in the game. I don't have a good excuse other than that.
But I can go back to work and have a better approach on doing a more complete wireless assessment than I would have if I didn't take 617. That said, there's a lot of parallels between Hacking Exposed: Wireless and 617, obviously due to the author being the same.
GSEC, GCFW, GCIA, GCIH, GWAPT, GAWN, GPEN, OSWP, WCNA, CCNA, CCNA Security, SFCP, SnortCP, and more useless acronyms.
Hopefully-useful stuff I've written: http://kimiushida.com/bitsandpieces/articles/