I just tried the leather finish for the first time, and it turned out great -- though it was not without trouble. Luckily I was able to salvage the job despite my mistakes.
The biggest problem you'll likely have is VERY visible lap lines if the glaze dries too quickly. Some things that can cause the glaze to dry too quickly:
1. A poor quality glaze
2. Glaze:paint ratio too high
3. Room too dry
I've read various tips about how to extend the open time of glaze -- mixing in an extender like glycerine, misting the wall with a little water right before you apply, etc. -- I haven't tried any yet, since I didn't learn of them until AFTER I screwed up and wanted to find out why, so I don't know how they work. But they might be worth a try.
The nice thing about this finish is that you CAN sort of "rework" it with a second coat and fix any serious problems you have without losing the effect. In the end, the result was absolutely awesome. It was just took a little extra work to get it there...