Thought I might but in my two cents.
Just picked up an R4DS that came with a 1GB microSD card. Been playing with it all day trying it out.
I must say, it really transformed the way I use the DS. No more carrying a bunch of carts around. All the games I want, plus a media player, built in cheats (if so inclined), and I've tried out a few homebrew apps.
Highly recommend this nice little toy.
Not trying to plug where I bought it from, but I'll just say I got it on Amazon for about $45 new with the 1GB card. Not a bad deal at all!