For Brisbane at least, the thing about Vodafone is to have a device that can to 850Mhz for UMTS (3G).

From experience, most of the issues that Vodafone Brisbane users face is when they have a device that only does 2100Mhz. Vodafone have done a lot of work into their 850Mhz, at least in Brisbane, and the difference in performance and signal strength between a device that can and can't do 850Mhz can be quite amazing.

Vodafone's 2G network isn't that great. Unlike Telstra and to a lesser extent Optus, Vodafone very early on invested in their 3G network. It was fine when the iphone was  a pipe dream and there wasn't that much data that was taking up spectrum, so they could see the excess capacity of Savvytel (motto then: credits never expire!).

So Vodafone customers don't really have a luxury of falling back to the 2G network.

For Viber, the Vodafone network generally is okay, but I would be wary using it as the main communication means.

Being in West End may make little infliuence. Its a relatively flat place and semi-densely populated. Being in inner city Brisbane doesn't mean you don't have black spots. Just ask those who live in Spring Hill.