I'd be interested - but I admit the cost can be a little hard to swallow, even with all the track time you get out of it.
On a social level, I think it's a great thing to spend a whole day riding/pitting with people of similar ability. Being friends off the track definitely adds to courtesy on the track, and that's something I appreciate a LOT.
I'm sure it's also more rewarding for the CR's to be able to work with fewer people at a time, and really get to see riders progress throughout the day, rather than trying to remember who is on which bike, and what they talked about last session
Putnam would be an ideal location for an SED (for me). I try to visit friends in the area when I visit, so a one-day event makes that much easier.