Too much of a risk. My biggest issues were that I was misled initially, and that I wasn't allowed to cancel my service on the phone even though I signed up for the service on the phone.
I had looked into external antennas but I'm not even sure there is a spot on the device to connect one. Even then I would have been out of the 24 hour refund period had I ordered one. And who knows if it would have gotten me enough of a signal anyways... potential waste of money.
I'm with us cellular now anyways, and without an external antenna I get acceptable speeds.