Personally I think huge numbers of megapixels is a waste. You need to be making one BIG ARSE print to warrant it. 6 megapixels is enough for most people, 12 certainly is.
I'd much prefer higher iso performance over more pixels especially as they are mutully exclusive anyway. (high pixel density is bad). It;s also more data for the camera to have to process and thus you get less shots to a card, less shots in your buffer and generally slower handling.
The Canon 5D is a real bargain, if I was a Canon guy that would be my pick even though the build quality is a bit suspect (by that I mean it's by no stretch a pro camera, due to the lack of weathersealing and so on but it's plenty fine for non pro (read beating on it) use).
I'd love a Nikon D3 as it has enough pixels (12mil) super low light performance and is super fast. It's also built like a tank but it comes at a price. The rumoured D3X is said to have 24 megapixels but personally I don't see the point, certainly not if it comes at the expense of low light performance and speed.
If I was shooting stuff that needed 20mil + pixels (eg magazine covers) I'd use the best tool for that which would be a leaf back on a medium format camera, not an SLR.
I'm happy with my D200, it's pretty well weathersealed, feels solid, has enough pixels (10 mil) and is fast enough (5fps with a decent buffer). Low light performance could be better (nothing particularly bad about it, but times move on) and a D300 would make a nice upgrade, but the extra cost isn't worth it as I've yet to find a situation the camera can't handle anyway.
My current favourite situation is when someone see's one of my better pictures and says "wow, you must have a good camera!". Hmm.... I wonder if when Michaelangelo finished the Sistine Chapel ceiling did people walk in and congratulate him for clearly having a lovely set of paint brushes?
People should spend more time learning how to take better photos than reading camera feature lists. A more expensive camera will not (in 99% of circumstances) result in a better photo. (although everyone should be encouraged to switch to SLR's if possible).
