The megapixel war is a distraction in many senses. There's only so much room on a sensor to cram those pixels in.

I'd be interested in:
- ISO/Noise performance
- AF Performance
- Metering and how badly the camera can't meter in conditions
- Customisation of kit to your needs

Unless you're pixel pushing, there's a very strong chance that you won't notice the difference. Only when cropping will it start making a difference. (I travel with a mobile studio with printing kit, knocking 6 x4's for cash. I used a 20D (8pmx), which was overkill then. I've now got a 40D (10mpx) which is just not worth it - the 20D was seizing in use unfortunately )

Unless I'm doing very serious work, pixel count is not the first priority for me (and even then I'm more interested in getting everything else set up as opposed to the tool I'm going to be using) .