If you've got the dough for a dSLR, do it. Too many reasons to count.
Yeah, try a bunch, find what works for you.
I shoot in the highest resolution possible, then downmix later. If you bought a digital camera, you can afford a decent sized Flash card to store your pictures on (before you upload them of course).
4 and 5 megapixels? Yeah, there's a difference. How big is it?I dunno, about 15 percent?
How much is it worth to you?
Buy to match your shooting style. I like a lot of manual control.