If anyone is wondering, I decided to give H2O a month 'trial' on my Veer, and the Veer shows that it's using H+. Mobile Hotspot doesn't work, but FreeTether does, and so I ran Speedtest.net from my laptop tethered via Wifi.

With 1-2 bars of service out of 5, speeds the result was 1.30Mbps down, 0.67Mbps up. This was in the Boston area, so other results may vary.

No idea what the monthly cap is though.