I don't have any recommendations for you, but here's my plan of action.
I have been monitoring my usage for the past year. I have an iPhone. I've slowly been weaning myself from my emotional attachment to it. Much exposure to WP7 and decent Android phones has helped tremendously. I use an average of 150 voice minutes a month, 20 texts, and ~170mb of data (although most of it is me diddling around, checking Google Reader, FB & Twitter, my device checking and downloading emails and notifications when I'm not near wifi). I'm always within wifi at work and home.
I'm going to start by getting a T-Mobile Pay As You Go SIM. If I can port my # to the SIM, great. If not, I'll port it to my Google Voice account. If I actually need data on the go, in a pinch, I can grab a Web Day Pass for $1.50. But for 11/12's of a day, I'm around wi-fi and so I'll get all my blessed Twitter/FB/G+/GTalk notifications.
I figure 2000 to 2500 prepaid minutes, costing me $200-$250 over the course of a year, should cover my voice and texting for a year. In actuality, I'm lazy at work and often don't use my desk phone, so I expect my wireless minutes usage to plummet. I should see savings of at least $650 a year from what I pay on AT&T.
If this all fails, I will probably look towards the $30 or $50 Monthly4G prepaid plans on T-Mobile (http://prepaid-phones.t-mobile.com/prepaid-plans) and go from there. Even if I went the $50 route, I'd still save $300 yearly.
The straw that broke the camel's back happened before today's txt plan news, but it's just becoming harder and harder to participate as the victim in this swindle.