For making phone calls & Google Voice, I've rather use a Bluetooth headset - it's much easier (and safer if driving - and, if I can figure out a secure & solid way to mount it solid inside the car as oversized GPS for navigation - with the screen saver disabled .... looking for the Car Mode apk that's on our smartphone but isn't on the Vpad7)
With a better quality (noise-cancelling is best) stereo corded headset - the sound is quite good, no Bose but it's good enough when we travel - it's easy to connect to any 3.5mm with a patch cord.
The compass/calibration aren't a problem for mine (HWver 107 with ITE) and it certainly isn't resetting or losing settings every few minutes - at least no popup about need to configure/calibrate or simply "losing" orientation.
I fine tuned all the related GPS settings and also run the GPS Status & Tool apps from the Market, so fresh positioning data are updated every 2 hours as needed.
As for using the Vpad7 in portrait mode once it started up, I'm using the VTL Launcher (link posted elsewhere in this (sub)forum - just "search") along with Widgetsoid from Market - which provided a lot more options to quickly access, change, turn off/on features as needed (i.e. reboot device) without going thru all the hidden menus (as if anyone will likely remember them) and this combination is making it less likely to swing or rotate 90 degree back to landscape mode or worst, turn upside down. Give it a try & easily uninstalled if you decided later that you don't want to use it.