I recently decided to do an informal survey of my family and friends around the US, of which I had literally hundreds of people participate. Not scientific, but interesting.
Without boring you all with the details, here's a quick summary: AT&T sucks ***IF*** you live in NYC, SF or parts of Chicago (and I'm sure some other "dead spots" around the country). OTOH, if you *don't* live in those places, AT&T is perfectly fine and people are generally very happy with the service.
Verizon, likewise, **SUCKS** if you are in one of THEIR dead spots (basically west of the Mississippi except for the actual West Coastline), and they generally got lousy marks for customer service in my poll, but the service itself is perfectly fine barring the CDMA limitation of no simultaneous talk/data.
Sprint -- who will almost certainly get the iPhone later this year -- got lousy marks for customer service, high marks for good prices/plans and utility phones (less so for smartphones). If you're a blue-collar worker out in the field a lot with a company-supplied phone, you LOVE Sprint and don't know what the fuss about iPhones is all about.
LTE generally is a non-issue to anyone outside of NYC and other mega-cities. It will not really be on the mainstream "radar" until later this year or next, when a) it's everywhere and b) it's cheaper!.
Conveniently, this will be about the time that the iPhone 5 or 6 (as the case may be) rolls out, and right about the time that everyone who bought an iPhone 4's contract is up for renewal.
Something to think about regarding LTE: it's not of any importance EXCEPT for people who move a LOT of cellular data around, and pay dearly for doing so. So if you're not one of those people, you're not really going be affected by that "revolution" too much except to the extent that more capacity on the network = fewer problems with calls and texting.
And hopefully prices will (eventually) drop for data. That was the #1 hope among my poll respondents.