We at Rangeforce have sprints and we just adopted Asana for it. While organizing sprints is fairly easy:
Having an epic (large task that is divided into multiple sprints) gets complicated when you need to assign multiple subtasks to a project. Like you're not going to go each task and assign it, that's like 4 clicks and some typing.
So what you can do is select the subtasks by click-drag or click+shift+click and drag them into the main task, then multi-select those and assign them to the project you want. Then drag them back. Only the last step has to be manual, but still pretty fast..
Asana is awesome. Super intuitive. Wish this was a little better too :)