Google Talk was one of the more promising applications from google. At the time it was released it was a like a breath of fresh air with an uncluttered and snappy interface, speedy startup and with better voice clarity than skype. But it looks like the project has been abandoned. There has not been a release in years (not counting the half baked labs edition). Features like group chat never made it to the main desktop application. While the google talk gadget and the inline chat in gmail helped in expanding the reach of the service, only the desktop client has the ability to make voice calls. In a sense google talk lives on as the gadget and gmail version but there are quite a few who mourn the death of the desktop client.
Also the libjingle library which allows you to interact with GTalk which was released with much fanfare in Dec 2005 has stagnated. The changelog indicates the the last release was in Jan 2006 and according to the svn log the last change was in Feb 2007.
According to the IM network statistics June 2008 released by EQO communications, GTalk has a decent marketshare in many countries. I'm not sure if they are counting the talk gadget and gmail chat uses, but I for one am sure that if they had given a little more attention to their desktop client they would have had a much better client as well as market share.
Google hired the lead developer of gaim (now pidgin) Sean Egan, persumably to work on google talk in October 2005. Though pidgin has had multiple releases during this time, none of them had support for audio or video. Pidgin team was trying to use libjingle to add support for GTalk audio but that effort has not borne fruit until now ?
So what exactly has Google in mind for Talk ? Will it be allowed to rot away and die or will Google surprise us with some innovative and awe inspiring features. Looking at the history of the project I think the former is far more likelier but that would be a sad day.
Update: In yet another case of neglect of the desktop client google launched voice and video support in GMail but there has been no comments about video support in the desktop client.