"Per month" ? Why not pay-as-you-need prepaid plans, such as the Wal-mart hotspot with no expiration featured earlier today?
Most users (including myself) use wi-fi most of the time, with some occasional network use.
Seems like a better deal to get that hotspot and tether as you need (4GB for $45) than this plan, unless you're a heavy user (which is impractical right now, given Sprint's overcrowded 3G network)
My only hope is that Wal-mart strategy takes off, and gets copied. But I'm not holding my breath.