Like MX727 posted, it is impossible for the CDMA iPhone5 to do simultaneous data and voice. This was Apple's decision, not the cell carriers. They wanted the phone to be smaller, lighter, thinner etc.etc. Verizon lied to you if they actually said that (or they are ignorant). To me this is a show stopper. I routinely talk handsfree on my device while using Google Maps turn by turn directions in my truck.

I don't think this new iPhone advances the ball forward. In fact, I think it is a leap backwards considering the technology built into existing smartphones. Forget about the lack of voice/data in the CDMA iP5, the GSM version has limited LTE radios as well. And it doesn't support European LTE at all. It doesn't have a NFC device. Also, I think battery life is going to be an issue. 8 hours in 3G mode? Wait until people have the phone in 4G. I don't really care for the Motorola or Samsung smartphones, but their phones have talk times of 21.5 hours and 15 hours respectfully.

I think I will wait for the iPhone 5S before I buy one.

Currently, there is no voice-over-LTE, so even an "LTE phone" has to use CDMA or GSM for voice. It looks like the iPhone 5 is unable to use LTE and GSM/CDMA simultaneously, so it downgrades to CDMA or GSM only during calls. CDMA is voice or data only, while GSM allows both simultaneously.

Samsung's GS3 (among others?) apparently has an additional antenna and/or different radio chipset that allows simultaneous 3G calls and LTE data, regardless of whether it uses CDMA or GSM for 3G. YMMV as there are different models of GS3 for different carriers.

Some roaming info:
Which iPhone 5 Lets you Roam...
WHICH IPHONE 5 FOR A GLOBAL TRAVELLER?

Still sold on verizon for a few reasons. The top reason being that Verizon will unlock the phone after 60 days (this alone is worth the switch for my international work). Secondly, their LTE network on my iPad performs magnificently... and fast so I'm looking forward to using it on iPhone five. Finally, their coverage for where I typically go in the states is so much better.

iPhone 5 only has one antenna. Thus the Verizon one will not do voice and data simultaneously.

I question how smooth the switch between LTE and CDMA will be too. These guys are great at marketing the phones without telling you what won't work as well as the previous version. Remember Antenna Gate?

May wait for the iPhone 6.