I agree we were given a leapster when our children were young, and it had a very very short life (because to be frank it was a bit crap). Their DS's have been played with for the last five years (by all of us too). But then I'd not buy a DS for a non reading child, so it also depends on how old your dd is.
I'd also not buy something that hasn't been reviewed, and that doesn't have a decent library of titles, as whether these things are fun depends largely on what is available (a big plus for the DS as it's been out for such a long time and has many developers, so a big range of different games are available).
i have preordered looks great and dd1 who will be 6 years old in aug on her bday she already has a ds only plays mario she got a leapster 2 for her 4th bday and luved but has outgrown now have seen lots of good games for this it takes explorer games going to get around the globe, and a couple of other games says it comes with a art studio and writing game already on it