Syncing? How did you have it set up precisely?
As to the speed, no improvement but degradation on my end. Still the same uplink speeds, but loading the iDisk listing in Finder for the first time takes about 20 sec. which is lousy. I do manual drag and drops. No bugs or lost files so far. iSync is gone from Lion, BTW, so not sure how your syncing worked before. iDisk access has definitely slowed down in Lion.
Obvoiously, they are pushing for in app syncing, totally bypassing utilities such as iSync. Sync Services are supposed to be gone from Lion as well. So I've heard.
I think so. No real issues with my iDisk.