I'm a current iPhone 3G user who is planning on switching back to the Bold. I think my biggest problem with the iPhone and why I'm switching back is that while it's a great device, it just isn't finished yet. I'm tired of wondering if Apple will make something like copy/paste a priority. The lack of background processes means no real IM until they set up their PUSH system in September. I have no idea how or how well this will work for notification programs, but I have my doubts considering how terrible MobileMe has been implimented to start.
The App Store has actually been something of a disappointment as far as I'm concerned. Way too much crap to wade through to get to the few gems in there, and the gems themselves aren't that fantastic. Again, the lack of background processes running means To Do programs can't remind you when something is due, thus limiting their effectiveness. The games I don't care about at all.
This is not to crap all over the device. It is a fantastic device. THe possibilities are limitless and one day it's going to be the best mobile computing platform on the market - I have absolutely no doubt. But it's just not there yet.
So, I'm going to switch back to the Bold for at least the next year (or two.) I miss having real IM clients on my phone, task lists that remind me when a task needs to be done, and a flat out better phone (the 3G is much improved over the first one, but BB's are still better).