I agree with Ian on DS, it sold very well in spite of the odds, and that is what Nintendo would most likely notice. Having said that, I don't think Nintendo is ignorant of the fact that it has more power in the handheld market than in the home console market. I think that's exactly why Nintendo launched DS so early, it knew it could get away with it and get a head-start on Sony.
With the Rev, that kind of strategy would be a very bad idea, so I agree that Nintendo should aim for quality rather than an early launch, but of course both would be better. Revolution will need a rock-solid game that proves the new concept, like Super Mario 64 did for the N64. Revolution needs needs to hit people with it's full potential right from day one. The DS failed at this (at least for me) because it didn't have a game of Super Mario 64s calibre to impress me. I bought the system with Wario Ware and Feel the Magic which are both good games and both made full use of the features, but they didn't provide a "complete" experience - you could play them and still not know if the touch screen was good for anything more than mini-games. Metroid Prime Hunters: First Hunt was encouraging in this respect, but it was still just a short demo.
So yeah, it would be better to have a great launch lineup in November than to launch in April with crud, but I hope Nintendo is putting an effort in to do better than November, and I feel that it should have been ready to launch sooner in the first place.