Ugh, I'm torn here...
I have an unlocked Galaxy Nexus from Google with T-Mobile's $30 prepaid plan. I usually use more than 100 minutes, so end up paying overages of about $10, so $40 total. If I switched to this plan, I'd be paying $55 (i use google voice for texting) and get 500 minutes, and unlimited data. I'd also gain better support, some random features like call-forwarding, maybe free nights and weekends? And unlimited data... although I haven't used my 5GB, this is partly because I'm careful about it KNOWING that there is a limit.
But tethering is a big one for me. I need to be able to use it in rare instances when its necessary. If there is no way to get around their tethering block... that might be a deal breaker.