I use M3 Real, v3.4X, with an 8GB MicroSDHC card. As of yet, the only problems I've ever had is with slow menus and the occaisional crash (probably from enabling soft-reset). So far, there's no difference compared to the 512MB, 1GB and 2GB microSD cards I've used. It even works fine with 1000+ ebooks and about 20 songs on it!