I'm always worried that someone at T-Mobile will notice that plan, say "whoa, how did that get there?", and delete it. It's just so much cheaper than everything else on the market.
Note that in ordering the SIM card I did not indicate that I wanted any particular plan. The $30 plan just "happened" to be available for that card.
Was I willing to wait for one week in order to lower the bill for a large recurring cost by 40%? Yes. But T-Mobile seems to be gambling that most people aren't.
I've been using this plan for about a month or so and coverage has indeed been a little spotty in my area but it's good enough for my needs. If you do want to try it out here's a tip port your number: do NOT do select the option to port during the online activation process. Sign up and activate your SIM FIRST and then call in to initiate a number port request. Once you've activated and signed up for the $30 plan with a port request, there's no way to get a temporary number while waiting for the port request to complete.
[1] http://slickdeals.net/f/6332098-tmobile-99cent-sim-card-sale...