They don't scratch our leather like they did the fabric furniture-I don't think it's the proper texture for that. The only real problem we have is when they run across it or jump up and slip, their claws sometimes scratch across it. We don't have any really bad, noticeable scratches, but there are some light ones if you look for them.
Make sure you get leather that has a really deep finish on it-so that is they scratch, the color underneath is the same as the top and it won't show as much. And it would probably be better to have a medium to light color instead of something like black.
We've had less problems with leather than we did microsuede. We had a lot of permanent scratches on that. Leather has been surprisingly resilient for us.
The cats aren't real crazy about laying on it without a blanket.