Erm, you need it for the official Web browser software. Also, the Cyclo is good, the Edge is a very nice clone of that. Other great available options are the m3/g6 real, the DS Top Toy, and the Supercard One (iirc has MicroSDHC support). The m3ds Simply / R4DS is also a very good option with quite a broad userbase, incredibly simple to use, decent support, etc.