My experience with the iPHone and AT&T:
1) The AT&T network is nowhere nearly as poor as advertised by Verizon Wireless. Service was actually good or better than VZW in many areas. Most of my problems occurred when I didn't upgrade the OS on my iPhone because it was jailbreaked. Once Apple started trying to get rid of the jailbreakers with all sorts of tactics, I bailed on Apple.
2) I find the sound on my Droid worse but acceptable. Many here report the same as I - it sounds like the person on the other end is talking through a small earphone at the end of a tunnel. It's fine but I use a headset most of the time so it doesn't matter. Also speaking through the mike requires you to be right on top - put it on your shoulder, forget it.
3) OS not nearly as polished as the iPhone. But the extensibility, multitasking and everything else made this a no-brainer trade-off. Apps are more polished on the iPhone but Android apps can be far more efficient and powerful. Apple's API limited to what they allow.
4) Apps in Market are virtually as plentiful (useful) as iPhone. If and when multitouch is fully enabled I can see Android being way more useful than the iPhone. It is already. It's not even close.
5) Hardware keyboard. This alone was the decision maker IMHO. I always wanted to keep the "sent from my iPhone" signature so I could prior excuse myself for embarrassing iPhone contextual spelling correction errors.
6) iPhone battery life much better than the Droid. At the same time let's not even compare the screen. My oh my, reading docs, especially small landscape, is stunning on the Droid.
7) A BIG DECISION MAKER: The iPhone OS is a disaster if you're a business user. It was amazing to download docs I left at home via the net onto my Droid, read them in any app or even transfer to my netbook or a local PC via the SD card. The flexibility itself is just fantastic, like the Blackberry and others and as would be expected.
8) No need for iTunes. The only thing it helps with that blows away the Droid is (a) backup of the entire device to the PC, and (b) Outlook sync. These are a pain but you can manage both, potentially, although not optimal.
If you want to go back to the iPhone, go ahead. At times I'm frustrated with my droid too. But there are so many times when I'm so glad I have it and deal with the frustrations, which I notice when the arise. Not so bad, I'll deal with the trade off.