- I like the fact that I can talk and surf simultaneously on GSM networks. You can't do that on current CDMA networks.
- I like the fact that I can easily pop the SIM card out and switch it to a different device without informing or asking the carrier. It's lengthier process with Verizon or Sprint, you have to get their permission, and they're fully aware of every device you're switching to, and will attempt to impose whatever charges or changes based on the new device.
- I like the fact that I see nothing more than an AT&T logo on my iPhone. It's obvious that Verizon is more of a control freak than Apple, and imposing their own App Store, VCAST, lockdowns, unified GUIs, and/or stupid red colors and themes on nearly all their devices including ones running on Android. I would actually be surprised if they at least didn't have their own icon on the Home screen that I couldn't delete.
- I like the discounts on AT&T and if you watch your bill closely, there's usually never a surprise. I can tell AT&T that my three iPhone 2G's don't use data, so remove it from my plan. CDMA networks in the US are notorious for tacking on extraneous charges, "inadvertent" billing errors, and nickel-and-diming you for everything they can. They're more strict and unyielding, and I wouldn't be surprised if they try to force in a data plans on even "smart" dumbphones.
If they knock most of these issues out, I'd switch. If they knock these issues out and add a killer feature, I'd break out of my contract. Other than that, I don't see it happening for me.