By keeping things relatively simple, Nintendo has ensured that XD is a fun and progressive RPG without any of the hindrances that dog lesser games. And that's the definition of good game design, so give the developers a pat on the back.
It's no surprise that battles are the main feature, but they've never looked so good. In Genius Sonority's last effort, Pokemon Colosseum, character animations were blocky and the character models weren't particularly impressive. Although XD makes use of the same engine, the Pokemon themselves have been refined and look much better than they did.
It's certainly a delicious slice of role-playing cake, then. However, the solid and well-produced RPG element seems to have resulted in the sacrifice of some features outside the main game (like those found in Colosseum, or even the old Pokemon Stadium titles). The Game Boy link-up feature is cool if you want to battle the Pokemon youeve collected in the GBA games or if you want to trade Pokemon between XD and FireRed/ LeafGreen, but there isn't much beyond this basic facility other than a couple of mediocre minigames.