Are more megapixels good ? The camera manufacturers at least want you to believe this, as that would help them sell more cameras. As you probably know, many megapixels alone are not enough. Some point-and-shoot cameras have 10 or more megapixels on a very small chip. The small sensor does not deliver the same image quality as the (much) bigger sensor you find in most DSLRs. A Canon 1D Mark III with 10MP delivers a much better image quality than a point-and-shoot camera with 10MP.
But more mega pixels are not bad when you have a good sensor. For example my Canon EOS 40D has about 10MP. This is almost 4MP more than my older EOS 10D (about 6.3 MP). The image quality of the 40D is better than that of the 10D. Technology simply has become better (and cheaper!).
The more mega pixels of the 40D allow me to crop some images and still have enough resolution for a good print.
Take this picture, for example:

This image shows a landing Black-headed Gull in an interesting pose. The Gull is unfortunately not completely parallel to the sensor, but this doesn’t matter here, as I just want to show you the benefits of more mega pixels.
The picture as seen here is not the best. The wooden bar is not the most beautiful and the out of focus gull in the lower left corner doesn’t make this a better picture, either.
Thanks to the 10MP of the 40D I can make a crop with about 5MP and still could make a good looking print of 20×30cm or even more of this picture.
Here is the cropped version:

This is a much better picture as it has no distracting elements. Of course I could also have cropped this image if it had been taken with a 10D, but the result would be about 3MP instead of 5MP, which is quite a difference.If you are photographing a lot of birds you will probably crop from time to time. It’s just not possible to get close-enough to many birds all the time. The more megapixels you have, the easier it is to crop.
Some may say this is cheating but I don’t think so. That picture was taken with my Canon EF 4/500L IS and a 1.4x extender. Isn’t adding an extender also nothing but cropping in the field ? One could also argue that using a camera with a crop factor (like my EOS 40D or Nikons D300) is nothing else but cropping. So for me cropping is absolutely ok. The only disadvantage when cropping with the computer is, that you loose data, whereas you don’t loose data with an extender.
What do you think ?