I'm back from my trip. The service from Mr. Simcard was great. It worked as advertised, and they sent me an SMS after I arrived to let me know I could call anytime if I needed help.

The only drawback was that my handset didn't automatically configure the APN; I had to set it up manually. Since I didn't have internet access at the time I just plugged in the values I remembered from when I was a VoiceStream subscriber and it worked fine - I had fast 3G pretty much everywhere I went.

I would use them again.