It's hard to say how many... I believe the media and web have sold the need for more pixels. Dito with "L" lenses when a tripod, a mediocre lens, and better technique would do a whole lot more for your pictures along with a couple of good books and practice. Not that anything is wrong with either of them (I do own a 10d and currently have one L lens and owned two others in the past - I own three tripods too). I'm not sure if people are just concerned about being crass or think a better lens and more pixels will make them a better photographer?

Sorry for the rant! My point is good lenses and more pixels won't make up for good all around technique. Plus, there's a point of diminshing returns with these. The better the lens and sensor (for a given format - the d30, d60, 10d, and d300 are all aps-c), the harder it is to get the most our of them. Unless, of course, you're in a vibration proof laboratory....

Here is a link to check out:

http://www.photo.net/equipment/digital/sensorsize/

Mike