I got one a few weeks ago. I got shouted at yesterday when I returned from a 3 day trip because my Mum had been unable to go on Dr. Kawashima's Brain Training for 3 days and he was going to shout at her ¬_¬
I had Metroid & Worms but Worms had less weapons on the DS version than the original '93 version that came on Floppy Disks so I was massively dissapointed and took that back and Metroid was a good game in theory but with a screen that small which you HAVE to use to control the gun on the touchpad and the design of the controls I found it hard to play for any period over 10mins, my friend also agreed I prefered Metroid on his original DS as it was a bit larger and easier to hold.
I can't recommend New Super Mario Bros, Mario Kart DS, Advanced Wars: Dual Strike or Brain Training enough though.
If you have a good enough WiFi signal then Mario Kart is endless fun because you can just do the online play if the real game seems too easy (which it did from the getgo for me)
Mario Bros - enough said really.
Advanced Wars is odd... it's like combining a calculator with risk but it's strangely addictive.
Brain Training kind of grew tiring quickly with me but I've been kind of busy recently so the only time I play on my DS is just before I go to bed... in fact I'm normally in bed so out of a sense of pride I refuse to do my daily test in case I get a bad result because I'm tired.
The only thing that really confuses me about the DS is the 'WiFi' which is used for Verses play. It doesn't really give you enough of an idea when you're using it for online (downloading content or playing against other players) and when you're just using it to connect to another DS. That aside it's a great little console.