How good is 10.2 megapixels for a camera?

All other things being equal, you will not notice a difference except for the larger file sizes for the same size of picture taken. If you aren't using the camera professionally, I suggest you concentrate more on features. These days, people seem more interested in big numbers (for pixel size) because it's the easiest thing to discuss around the water cooler. IMHO, anything over 6 MP is a waste unless you're getting a bargain.