We just bought one for my DS's 6th birthday last week. I'm not a huge fan of videogames, so we treat it like his old Leapster and generally buy educational games. (For those who think this is crazy, I assure you that PG kids can have just as much fun on quests while doing math as they can playing Sponge Bob.) We are also letting him get LEGO Harry Potter, since he's in a HP stage.
So far, he really likes BrainQuest Grade 3-4. He also has Brainquest 5-6 and he likes it, but it's not nearly as easy since he hasn't covered most of the subject matter yet. There's also a Smartbrain 8+ that was just released this week. Someone is giving him in another week or two (delayed birthday present), so we'll check back and report how that one is, too.
We were also looking at Spelling Challenges, but I think we're going to wait until the Scripps one comes out in October.
