I will be making the switch soon. I will be paying an ETF in the $250ish range on 2 different phones to make the switch. Fortunately I'm able to sell both i4's phones and a 3G to more than cover the switch to VZ and purchase two new iPhones.
Our in home reception is awful with AT&T and it's been driving my wife nuts since last June. She's a former VZ customer who hasn't been happy since I convinced her to drop VZ a couple of years ago.
By the time my contract is up, LTE iPhones will probably be available on both AT&T and Verizon. At that point I will re-evaluate and decide whether to switch or not. SO MUCH can change so quickly in the industry.
I have about 21 months left on AT&T, so it won't be anytime soon. I'm fairly happy with AT&T service in my home area (South FL), it's only been a little dicey in Manhattan, and parts of downtown Chicago.