We do rotate at Sloan. The amount of time is very flexible...I traded all my time away, while some residents have done around eight months or so. From what I hear, it definitely helps with the hem/onc matching, especially since our own program is relatively weak.
One of the nice aspects of a big residency like ours is the ability to trade with other classmates to get the training you want. I did a fellowship's worth of ICU time, others did a crazy amount of hem/onc. For people who know what they want to do (as long as it isn't GI) our system is great for getting its people into strong fellowships.
The matches into Sloan are great, but they're definitely not something we take for granted. We've had matches our last two years, but these were exceptional cases. I know both these residents well and they were both really remarkable in a not-every-year sense. But it's nice that we're beginning to set a precedent.