I do think it's advisable to have more pixels that the one you really need.
If you only want to watch images on a PC screen, let's say a 1280x1024 one, a 2 MP CCD is enough for the 1.3 MP of the screen.
But, if your original image is a 4MP one, the software that shows the image is going to put pixels together to make one 1.3 MP image on the screen. This means that some "wrong" pixel (the noisy one) has to struggle to stay on the image with the good one. This process is going to minimize defaults in the shown image and thus, it make sense to say that the image will be better.
That is said thinking that all software are equal

(who says bill ?).
I thing the software is going to make the difference in the year to come and really make the extra-pixels worthwhile. There are already settings on Digital camera that let you choose you're preferred image setup (color saturation, contrast, ...). It is sure that these sort of algorythms will better work with more data = pixels.
Now the problem is: how many too much pixels for your application ?
I thing: the better the camera, the less pixels !
But it seems that, currently, the best camera are also the one with the more pixels...
So go back to basics: choose the best camera for your application and your budget. Be sure the results are OK for you with some tests and preview. Then look at the number of pixels, these are enough to please you