I try to take one workshop a year - I find that these trips give me the opportunity to go places where I might not otherwise go. For example, the last workshop I went on was an Escalante Canyon backpack - a week in the canyons is something I would never attempt by myself.
I also find that these workshops are a great way to meet other people interested in photography; alas, the majority of the people on the last couple of workshops have been non-analog () folks. A few were still hauling around 4x5's like myself, which was nice.
And, they're just plain fun!