There is no doubt something like Canon's 16 megapixel monster DSLR
produces outstanding images.  But are megapixels (when you work in
smaller increments) that important?  Case in point, the jump from
6-8.  There are many people out there fretting about whether they
should trade-in what might be a two year old camera (eg, Canon Rebel)
for a Rebel XT with it's 8 mega pixels.  Will they see a major gain
in quality?  If they do, is it more likely to come about because of
other improvements, like noise reduction?
If you shoot a picture with an 8 meg camera, then back the camera off
distance wise another 13%, the pixels covering the image in question
are now the same as if you'd shot the picture from the original
distance with a 6 meg camera.
But I've done the tests and the results do not show that dramatic a
change in resolution.  So if there is any major gain
seen by going from 6-8, it has to be due to more than just an increase
in pixels, in other words the camera and it's sensor, it's processing
has been improved.  Also, what kind of pictures are going to benefit
from the increase?  Some subjects (not many, but some) don't have the
extra detail at the limits of resolution that would be revealed by the
incremental improvement in resolution going from 6-8 megapixels
provides.  Meanwhile, it seems the next jump for the middle line
cameras, Canon 20D, Nikon's successor (whatever it is) to the D100,
maybe Olympus's replacement for the E1, will be over 10 megapixels
which at least will provide a demonstrable improvement over a 6 meg
camera.
-Rich