I am in the same boat as you. Actually, I still have ATT and an iPhone, but got the Bionic for the wife (who had ATT and iPhone) and she is not happy with the Bionic. I keep telling her to wait for the OTA, but that may not change her opinion of the phone.
However, back on topic, I tried to get the 4G plan upgrade from the phone, and it would not go through. Called CSR and they said that it did go through...hmm. Anyway, I asked if there was any chance to get Unlimited data and he said no. I asked about my case...if I switch from ATT -would they incentivise me to leave me ATT w/ unlimited data to come to Verizon? He said no.
At this point, I am waiting for the Galaxy Note, and am hoping that I can keep my unlimited data with ATT when I switch (not fully confident in ATT). However, I do like Verizon service better...The signal at our house is great, while I need a microcell for an ATT signal which means I cannot get a signal in my own back yard!!!