I just got a 3ds a few weeks ago, and while waiting for some games in the mail, I realized I had a new unopened dq9 game that I had forgotten to get rid of when I sold my ds. So, I popped it in to see how the 3ds handled ds games....
Long story, short.... I racked up about 60 hours while finishing the main story quest, and absolutely loved it. It sort of renewed my love of jrpg's like the old school ff7-9. The graphics really don't seem that dated, and while multiplayer aspect doesn't really work anymore, you can still access the daily DLC for different outfits and weapons, which is cool.
Also, while I've finished the main story line, there is still tons and tons of stuff to do post-game, so its well worth the $12 or so.