Ran it in March for the first time. I was captain of an 18' rig but I took my kayak thinking I'd paddle more than I did. 18 of 21 days were spent rowing......which I absolutely loved and would not have done it any other way. However, yakin' wise......I'll take a different boat next time. I've seen many debates on the buzz about "playboats vs. river runners" for paddling the Grand. I took my playboat and wished I would have took a bigger/faster boat. I'm NOT a hardcore playboater by any means but I can git r dun. Some of the juicy-est, nicest, fastest waves I've ever seen were just not possible to get on, I tried my dambdest on a few and they were too fast. Either that or I'm just a wussie.
Add the comfort factor with a bigger boat cause you'll be in it for 6 hours (on average).
Day hikes. I recommend getting a "day hikes from the river" book (can't remember the author). Nankoweap, Thunder river, Deer Creek, Matkat, Havasu are a MUST, IMO. Elves Chasm is really cool and easy.
Planning for beer consumption can be one of the toughest decisions you'll have to make!!!!
Good luck with that one.......