You are smart asking people's opinions and trying to get information on providers. Just remember, you get what you pay for. My mother-in-law resisted both my and her daughter's suggestions NOT to go with the cheapest provider out there (was looking for a multiple phone *family plan) and now she hates them and is stuck. I honestly think she didn't choose one of our suggestions because they were different and she didn't want to show favoritism... goofy woman. Anyway, that is neither here nor there but I just wanted to make sure you did a lot of research and didn't let the bottom dollar be your deciding factor.
I have had Verizon since before it was Verizon (remember the little pink alien from PrimeCo?). I have had incredible service from them and overall am very happy. Sure there are billing issues here and there and sometimes something gets a little sideways in service (big Verizon blackout a few months ago) but overall things have been great. Verizon always steps up when there is a problem and they fix it right away. Also, when I have had an unusually high volume month and gone over minutes (death in the family, talkitive teenager, etc.) a quick call to Verizon Customer service and a humorous "HEEEELP" plea always results in a GENEROUS amount of bonus minutes to prevent your phone or any on your plan from going over.
So there it is... my vote is Verizon for their stability in service (RARELY a dropped call) and their CUSTOMER service (for the customer!).
Also, hee hee, check with each provider to see if they offer a discount with your employer. I know V offers a LOT of discounts.