I think that just a few things would make it better...

I think that by making attatchments go though gMail it would free up server speed while IMing... Also, allowing video feed would be greatly appreciated... Another great thing would be mass invite. I think that gTalk would be the best client in the world, if it was ported to *nix and mac! Someday V_V

This is just my take on a little program I have been using for only about a month, lol.