I'm in Mercer County, and I always have 3G coverage. I travel a bit throughout NJ and haven't yet had a signal failure anywhere in NJ and anywhere specifically in central NJ.
I've hit DE, PA (Philly and suburbs), NYC/SI/CT, and Westchester NY without signal fail. I've been able to leave SprintTV on continuously throught the area.
3G Speeds have all been good, except peak time in Manhattan caused slow uploads.
4G in Philly (and 'burbs) and at Newark Airport have been home wifi fast. SprintTV is incredible when in 4G coverage.