I have skypeout but don't use it so much (IP latency from here to anywhere is 150ms, across the pond it's 250; add to that skypeout's latency, and it's just not worth it).
I've been using skype for about a year -- it's very handy if you're not a supernode. The OS community wants folks to use other VoIP protocols, but no solution has the penetration and front-end simplicity of skype. It just works (and it's encrypted).