Classpass has come to Seattle recently. It's $99/month for as many classes as you like. You can only do 3/studio/month, however. Here, that's a little less than you'll pay for a monthly membership at the Y, and about half what you will pay for a "nice" full service gym or unlimited classes at a high-end studio that offers a single style of class (so flywheel, pilates reformer, etc).
I mostly signed up because I've been trying to do one flywheel class and one yoga class (as cross training) per week. Flywheel is about $30/ride. So, I figured that if I did 3 flywheel classes and even one other class, it was "paying" for itself.
Then I realized that it's not all classes at every studio. So, I haven't been as consistent with flywheel as I'd like (usually the 4:30 and 7:15 pm classes are included). At first this was a HUGE bummer and I considered dropping for just that reason.
Then I got overmyself and have been having fun trying all kinds of classes. I like that pretty much wherever I am in the city that day, I can find a class. This week I have a trx class, a kettlebell class, flywheel, and barre. I'll probably do another 60 minute spin class if I can get into the one I want.
I also love that I can take it with me when I travel. So, last week while I was in the bay area I did 3 barre classes and a spin class. Which is SO much more awesome than working out in the hotel facilities, esp since I can't run right now.
I think if it's your only excercise outlet and you really prefer to have a routine down, you might not love it. But, if you're a runner and tend to supplement your running with a class here and there, and you like variety/like to mix it up, you might get a lot out of it.