I'm thinking if they come out with a better/newer version later this year or early next year, I can sell an 8GB model easier than I could sell a 4GB model. Whether that's true, or whether I wasted the extra $100 remains to be seen. Chances are I'll keep this beauty for quite a while though.
I can see why many people would go right for the 8gb, like jbaraga's comment to not want to carry around two devices. It doesn't matter for me, because I carry around things in a purse anyway. I have other pda phones with tons of programs and 1gb storage cards that aren't even half used up, and I also have a 4gb Ipod so I often have two or so devices on me at any given time. Hence, the 4gb is fine for my situation. (although LOL, as I'd have picked up an 8gb if one had been in stock)