I haven't done any of the exchanges; the timing just hasn't been right. I would certainly consider the next postcard exchange - the suggestion for a quarterly (or seasonal) schedule would be about as frequent as I could possibly manage, and even then I'm sure I'd only be able to participate in some.
As for prints, it's a bit too much for me to deal with, both in getting mine done and sent, and figuring out what to do with the ones I receive.