[galaxy-user] "spot" EC2 instances for Galaxy?

Hi I'm wondering if anyone has had experience running Galaxy using the Amazon "spot" EC2 instances? These instances are charged based on a bid placed by the user, and only run when the bid exceeds exceeds the current spot price. In other words, you pay a significantly reduced rate for cloud capacity but it runs intermittently. This is OK for certain applications but I'm not sure how that will work for Galaxy. Specifically, I'm interested in using Galaxy for Tophat analysis of RNA seq datasets. Any insight that anyone has will be helpful. Thanks! Andy