Blink (http://icanblink.com) is ok as a client. I'm not 100% on the interface, but it does seem to work well without crashing. It's gpl, and it does seem to have some momentum behind it.

There's one called simply "Telephone" which is very simple, just a textbox to call. No contact list or anything. (well, it wasn't much in december, since then they've moved from code.google to github: https://github.com/eofster/Telephone)

Gizmo5 is a crashy piece of ...something. It's the only app I've ever had on osx that has crashed so hard it's needed to be reinstalled. Several times. OTOH, you can't get it anymore, and Google is shutting down the sip service behind it.

any idea how to configure Blink for GV SIP? I used +1[my number]@sip.voice.google.com and GV password but keep getting auth errors.

You can't register Blink for GV as an endpoint. You can use Blink to call a GV number via SIP (example here: http://truvoipbuzz.com/2011/03/make-unlimited-sip-calls-to-g... ) but you can't set up Blink as one of the numbers GV calls.

That's the missing piece I mentioned at the end of my article and has been made in several other comments.

Thank you for the clarification.

That's the crux of the article -- the sip in question is inbound sip -> gv # -> PSTN not sip client <-> gv <-> world

And at length, linked from the article: http://blog.duh.org/2011/03/so-google-voice-sip-is-actually-...

You might try VoiceMac from http://mrgeckosmedia.com/applications/info/VoiceMac . I've not used their SIP support extensively, and it's primarily aimed to be a Google Voice client, but it might suit your needs.

I also don't know if the version on the page is the latest beta, or simply stable.

The developer has been quite responsive to bug reports, etc.

Seems that the latest beta is at http://mrgeckosmedia.com/VoiceMac.zip with "lots of fixes."