It's not whether it has a revenue stream or not. It's the opportunity cost of the maintenance overhead on other Google products. Google is trying to become an organization that is very focused on a few big things. So the question is really "what percentage of Google's profit is derived from Google Voice?"

It's still a US-only service after many years. If it were lucrative, they probably would have moved it into other markets by now.

As much as I would like to use it, their desktop client has never worked for me so I use Skype instead. Similar rates, much better client. But your point around revenue is definitely a good one. I wonder how much it actually generates.

I suggest you install the plugin variation and try it through Gmail, at least if that is at all a viable option for you. It has been working quite well for me both in 64bit Debian testing and Win7 on 64bit.

I use if for international calling on my phone.