My friends who shoot Canon had to deal with these issues long ago. Nikon shooters are going to have to get used to it, or hold on tight to your 12 MP camera - you can pretty much accept the fact that Nikon is going to increase megapixels in the entire line as it refreshes the models.
#2. "RE: Increased MP's and sharpness" In response to Reply # 0
That's as good an explanation as I've seen on the subject. As with anything optical, the greater the resolution, the more it reveals the flaws of the operator and the mechanics of the device itself. It took me a few days of hard looking at my less than sharp images to realize it was motion blur (in spite of using VRII lenses). Once I increased shutter speed, and carefully watched the focus point, images got better.
#3. "RE: Increased MP's and sharpness" In response to Reply # 0
There is some misunderstanding, and some mis-information so far. The "sharpness" standard for depth of field is based on taking a 12 foot wide subject and viewing it on a 10x8 print at 12-15 inches - and being prepared to accept an edge blur image of 1/100th of an inch. This is not a particularly high standard in 2011. Digital senors are prone to moire in fine detail subjects - and many cameras incorporate an anti-aliasing filter to reduce the possibility of moire. This filter reduces sharpness. You have the camera options of pre setting camera sharpening for what you think is an average result for your needs, or leaving sharpening at minimum until the final enlarging stage. Sharpening as the last step generally gives highest final sharpness - but involves extra work which many do not want to do with every photo. Learning what is going on in the camera processing and post processing gets the sharpest pictures - but you have to work to get the highest sharpness, particularly when making big prints. Moving in a different direction file sharpness is part made up from lens resolution and part made up from sensor resolution. Improve sensor resolution and you get more resolution from any lens; increase lens resolution and you get more resolution from any sensor. How much resolution improvement you get depends part on the lens and part on the sensor. How much resolution you can get (often more than you need) depends on many things including sensor ISO, how old the sensor is, MP, lens quality, lens aperture and control of camera shake. Most modern cameras (including 6 MP bodies) are more than good enough for a 10x8 inch print. How much resolution you need depends in part on print size. Generally, as with many things in life, to achieve the highest quality photographic results the more you have to improve your skill level.
Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.