Had verizon for about 7 years (first cell phone). Only problem I ever had with Verizon was that they didn't have great coverage in some of the places I usually go to, so I would end up on roaming a lot. But other than that they were great.
When I moved to my current job, Verizon had no coverage here, so I switched to Nextel. Has some ups but also some downs. Nextel has great customer care, good coverage areas, good prices. Direct connect is very cool. BUT their no roaming network blows. Seriously, there have been numerous times when someone will try to call me and the call will go straight to my voicemail. My girlfriend and I tested it once, she called me a few times while I had a full signal and about half of the times my phone didn't even ring just went to my voicemail. That stuff pisses me off. They need to spend less money on marketing and nationwide direct connect and more on improving their network.