I said I would and I did - got a R4 for my NDSL! Very handy little thing, it's was definitely worth the wait and the money! The sound quality of mp3's aren't that great but oh well. It's easy enough to convert movies into a format the DS can play so I can get into bed and watch my anime ^_^ It can also read text files and dum dum dum.... play homebrew games! Great fun!
It is easy enough to use. After a false start everything went smooth afterwards. It doesn't fit as perfectly as other cartridges (you just need to push/pull a little bit harder at one point) but otherwise it's fantastic! The menu system is easy, it is well presented and works fantastic!
I'm perfectly happy with it and would recommend it to anybody with a DS *wink*