I use this and it's great! There are over 2000 games to choose from and tonnes of homebrew (I recommend lameboy for GB/GBC, DS Organize for web browsing and Nitrotracker for music editing. Also, Pocket Physics is an EXCELLENT game - Nintendo would have made a lot of money with this idea!. You'd also think that a product like this will not have much support - that is so totally wrong!!! There are frequent updates of the " R4 kernel" that fix bugs encountered on games. Also, Rominator is great for organizing your games and there's a great website somewhere on google that converts to dpg (DS movie format)

I use a 2GB Sandisk M-SD and I've had no problems. I can hold 30-60 games on there, plus homebrew, plus a movie

CONS: Homebrew will require downloadable tools to make it function, no cheat support on mac, games become less addictive - when there are loads, you give up on games more easily.