PdaNet lets me use my phone as a modem over a USB cable easily enough, after installing the OS X PdaNet driver for the USB, and enabling USB debugging on the phone. The USB cable keeps the phone charged which is a help, as the battery can drain pretty quickly. I'd had troubles getting BlueTooth DUN (dial-up networking) going, but this time something clicked.
With PdaNet running on the phone, I created a new BlueTooth profile on the Mac's Network Preferences panel. I used "Default" configuration, entered "#777" for the phone number; I did not need to include my Sprint PCS account (email address) and password. I then hit "Set Up Bluetooth Device".
When I started PdaNet it turned on the phone's Discoverable feature for 120 seconds, and the Mac saw it this time. The Mac asked to confirm the pairing password, and a notification appeared in the top of the Evo's notification bar, so I pulled that down to confirm.
On the Mac I hit "Advanced" and set the Vendor to "Sprint" and the Model to "PCS Vision" (the default), and let the other settings take their defaults.
Back in the main Mac Bluetooth panel I hit connect and after a few seconds of saying "connecting..." it authenticated and made the connection.
This seemed to work fine. But when I tried to reconnect, I could not. It almost appears that I have to re-pair the device, and then Mac gets stuck after doing so spinning on "Gathering additional information about your device." Is it really this stupidly difficult?
A subsequent attempt did complete the re-pairing and OS X demanded my admin password to save the changes. Seems pretty flakey, but I guess that's Bluetooth.