I was under the impression Sprint always charged extra to tether with a laptop? If the price includes BES access and unlimited tethering then it's not all that bad - in fact it would be the same as T-Mobile. With T-Mobile though, they have the BIS only option for $19 with unlimited tethering. That's the sweet spot for me - 50% of the Sprint rate in that case.
If Sprint had international roaming access on every GSM network like T-Mobile, and reliable billing/customer service then I'd be all over paying the $39 for the faster speed though. Don't think either will happen too soon though.