Same here.  I was with PrimeCo, which was bought by GTE, which became Verizon.  My "old" PrimeCo plan wasn't compatible with Verizon's new billing system so I kept getting billed incorrectly.  They had to manually adjust each bill every month.  They "fixed" this by switching my old plan to a new plan that was compatible with Verizon's billing system.  Thing is, they started me up on a new 2 year plan when they did this without notifying me.  When my work gave me a phone, I cancelled Verizon.  They hit me with an early termination fee of $275~ and reported me to a credit agency.  I never even got a phone from Verizon.  I bought a used Nokia off eBay at the time, so clearly the fee was ridiculous and certainly reporting me to a credit agency was uncalled for.  They said that by simply paying the first bill once it was switched over to the new billing system that I agreed to the terms of the contract.
My experience is with Verizon, AT&T and Sprint.
I will say that Verizon has the best network.   But I will NEVER EVER go back to them after what happened to me.
AT&T has the best customer service, but the worse coverage EVER.  
Sprint is a good happy medium.  Customer service is good, but it's based in the Phillipines so the connection sucks when calling them (ironic, right?) and there's a bit of an accent you have to deal with.  Coverage is better than AT&T, but not as good as Verizon.
Sprint is also dirt cheap.  I have a $129/month plan that includes two phones, 1500 minutes, free calls after 7 PM, unlimited data and text and unlimited cell to cell calls on any network.  
The phones are also reasonable too.  I picked up the Android based Samsung Intercept for only $99.   Other than the fact that the camera lacks a flash, this has to be one of the best phones I've used and I've used Blackberry, Windows Mobile based Motorola and iPhone.  Of course, the Android OS has a lot to do with that, but it's nice to have the flip out full QWERTY keyboard.  Too bad you can't get E*Trade and Bejeweled Blitz for Android, but there's no shortage of apps.  I downloaded 25 free apps just within the first 24 hours of having the phone.  
