I have used the Magic Eraser on my 911 turbo's steering wheel to get some nasty shininess off of it. Initially it worked great, the steering wheel came back to a nice matte finish, and looked good.
Fast forward a few months and I noticed that the areas I'd cleaned were getting shiny again. I broke out the magic eraser, went to town and it came back, but not as well as the first time, and I noticed significant discoloration of the Magic Eraser pad.
And, within a couple of weeks, the wheel was shiny again, especially in the heavily shiny spots before that I'd worked on hard. I talked to a few people, (leather master, leatherique, etc) and determined that yes, I'd damaged the top coat and the exposed leather was not standing up to oil from my palms and sweat at all.
I have leather master and leatherique, and I tried both, but they are not designed to repair the top coat. (actually turns out both have products that can do that, but they are not part of their normal consumer line)
It didn't take much. I would definitely not use a magic eraser again.
I spent about $100 on various products and the steering wheel looks great again, but it took a LOT of work to get it there. Roger Koh at the Leather Doctor has a really good set of products and knowledge, and those are the ones I ended up using to really fix it.