Unfortunately the desktop client needs some work, and AFAIK it supports only windows.
And another thing I don't like about Google Talk is that last time I tried, it had no support for multi-user video-conferencing. Neither do the free Skype accounts, but I think on Skype you can have a video-conference with up to 4 users.
So if Google is going to put some resources into GTalk, then it will kick-ass (you'll just tell your friends / colleagues to download the client and to use their GMail account for login), or just use the GMail web interface (which currently is more capable than the stable desktop client :)).
Google Talk runs in the browser. I tried it on Windows and Mac without problems. Actually, we found it to be more reliable than Skype at low bandwidths.
And another thing I don't like about Google Talk is that last time I tried, it had no support for multi-user video-conferencing. Neither do the free Skype accounts, but I think on Skype you can have a video-conference with up to 4 users.
So if Google is going to put some resources into GTalk, then it will kick-ass (you'll just tell your friends / colleagues to download the client and to use their GMail account for login), or just use the GMail web interface (which currently is more capable than the stable desktop client :)).
Otherwise there is no good alternative to Skype.