Although megapixels is not the total picture so to speak, it does make a difference if you are comparing apples to apples, rather than apples to oranges.
A newer point and shoot with 12megapixels will most likely produce better quality photos than an older point and shoot with 6 megapixels. You will see the difference in enlargements or side by side on a computer. More editing can be done on a 12 megapixel image than a 6 megapixel image before pixellation or noise occurs, too.
The same holds true for DSLRs. A lot more editing can be done on a 15 megapixel image, than on an 8 megapixel image and you can easily see the difference in sharpness and detail, especially if you are shooting something with a little texture in it. Even between a 12 and 14 megapixel photo it is possible to see the difference.
So, although megapixels may not be the only factor in comparing cameras, it is an important one for many shooters that are after detail and texture, as well as doing enlargements or editing.
I would note that of those that deride megapixels, I am sure that none of them are pros using an older 6 megapixel Canon Rebel.
skieur