Welp... I couldn't help myself. Was able to get a 16gig iphone 4 today at Walmart. I also don't use a ton of data, so I dropped my plan down to the 200mb one which will save me $15/month. Still not sure if I want to sell my 3G or hold onto it as a backup in case my current phone ever breaks, but who knows.
All I know is that the 3G to 4 jump is huge, and I'm pretty impressed. Now that you can set a background AND lockscreen background, the only things I really need to jailbreak for are SBSettings (a big deal), 5 icon bar, and winterboard for custom icons and SMS tones. When I set it all up I restored from a previous backup and everything seems to have gone fine with that. It ported over my emails and texts which is what I needed.
The camera is awesome and a HUGE improvement over the 3G camera, and the video recording feature on it is pretty slick. I doubt I'll use it much, but I may since it works so well.
Can't say anything for battery life as I just got it, but I'm hoping to at least get 2 days out of it as I could barely make it a day w/ my 3G. If I don't have to charge it every single night I'll be happy.