Well, I use it! And more and more of my IM contacts are too. Why? GMail. You see, GMail has GTalk built into it- so if you leave GMail open in a tab all day long, as many are wont to do, then you end up being logged into GTalk for as long as you've left GMail open.
At first I was sceptical of using GTalk through GMail. But I have found that the convenience of having IM and email all collected into one tab of my browser, PLUS the benefit of everything being indexed and searchable, makes GTalk a suprisingly viable IM solution. Ditching AIM was easy since most of my friends have GMail accounts!
So, now I am on the other side of the fence from you- The way I see it, if AIM/MSN/Yahoo!/etc were built into GMail then I might use their services more. You see, I used to use AIM all the time, but now I just leaved it logged in on one of my PCs. I occasionally check it to see if there have been any messages sent to me. Nowadays less and less are coming in via AIM and more and more are being GTalked.
Has anyone else had this experience as well?