Just thought I'd give a quick update on my Straight Talk experience after a couple more months with them.
They appear to now be throttling rather then cutting off people's data. Obviously, this is way better then their previous practice of simply turning data off inexplicably. However, as before, one friendly phone call to them with your woes and they immidetely unthrottle your account back to full speed.
I've had to do this exactly twice. Once when I went over 4GB without calling them beforehand, and once when I did so right before the end of the month. When I renewed my service I was still throttled, so renewing doesn't seem to reset the throttling.
Again, in both cases, I simply gave them a call (from a different phone since reversing the throttling requires a series of restarts with your iPhone) and all was fixed immidetely. I wasn't teathering, I was very polite, and they reversed it right away. Really no big deal, and if it makes them feel more secure whatever.
Couldn't be happier with Straight Talk and am currently getting 7-8MB/s on my iPhone 4S. Hooray for $45 a month!
By the way, I highly recommend forwarding all voicemail to Google Voice. The transcribed visual voicemail is way cooler then Apple's any day! I simply put the google voice app above my phone app icon and followed Google's instructions to forward my number's voicemail to theirs. Works a charm!