i have one friend with tmobile who lives in the Linden area and he says its ok. however everytime i had tmobile years ago, it was horrible indoors. outdoor coverage was ok at best, nothing like att or verizon around NJ.
Monmouth Junction area: it's been a while, but last time I tried T-mobile, indoor coverage was zero. Online coverage maps haven't changed at all since the last time I tried.
It's a shame, because if the coverage were halfway decent in this area, I would totally switch.
My experience is that when the coverage maps say "Good," it's actually poor. And "Satisfactory" means pretty much nonexistent.