Update: I called into Sprint BB support, and they told me that I needed the Phone-As-Modem option on my account. I double-checked that this was not the pay option required to tether regular phones, and the gentleman assured me that PAM was free for BlackBerry customers.
Yeah, I didn't want to add the extra $40 plan since I was told it was included with BB Unlimited. That fact is actually what sold me on dropping my T-M BlackBerry service and going back to a converged device.
Sprint allows it for free if you have BB Unlimited, you just have to make sure you get PAM provisioned.
So you can confirm that it comes with the Blackberry Unlimited plan? I would prefer to sign up with Sprint instead of VZW because I am a current Nextel subscriber, so no early termination fees apply....