When I reviewed the original ZTE Open last year, the Firefox OS experience was -- to put it modestly -- rough around the edges. The device was stripped down even by the standards of low-end phones, while the software was missing features other platforms have had for years. You didn't even get new email notifications, for crying out loud. Jump ahead a year and it's another story. The Open C is a much more powerful device, and Firefox OS has received a few vital upgrades. But does that mean Mozilla's web-based mobile software is finally ready for prime time? I spent two weeks with the Open C to find out if it can hold its own against budget rivals -- and to see if I'd be comfortable using it as my only phone.