Hmm, Settlers of Catan on the DS - it sounds too good to be true. But actually it's not bad - a fair representation of the game, a little bit fiddly, and a few times you wish you could skip sequences they make you wait for, but overall pretty good. The individual games are good, with random board set-ups and intuitive controls (no buttons, it's all stylus-based), and the campaign is tough but fair. The only thing i found a little frustrating was that the opponents ALWAYS pick one of YOUR hexes when they roll a 7, so they always rob you, not the other computer players - which is a bit biased, especially as the opponents are no slouches! I found that if you just don't ever trade with them (unless YOU need something from THEM), it slows their roll a bit!
Overall, a fair representation of Settlers on the DS which I've given 4 stars mainly because the mechanics seem to have got it right.