[quote name='mkelehan']I played it through, and I honestly think $3 is worth it to upgrade to having a map on another screen. I was looking at it all the time.[/QUOTE]
I would agree. I bought it for GBA at release after I read IGN's review that the games were basically identical. The GBA version was $5 less, so I figured, what the heck. But yeah, I was flipping back and forth between the map and regular screen over and over, so the DS version is definitely the way to go.
Be warned that this game does get pretty tedious, especially in the second half. It's not as much as Juka and the Monophonic Menace -- which is the other Orbital game that came out at around the same time, and used the same engine -- but it is definitely not on par with the Metroid games.
But for $3 and the right set of expectations, you can't go wrong.