Google Talk will implement all the suggestions from this page dedicated to Google Talk suggestions/inquires. After implementing file transfer and voicemail, Jeanne DeWitt says — “Now, we’re off to the next version. I can’t tell you what your #2 and 3 suggestions were, but I do know that they’re on the way. Also, look for more improvements to the Help Center and Talk Help Discuss group.”
While Google Talk is available only for Windows, Google will release versions for Mac and Linux. Microsoft doesn't intend to release Windows Live Messnger for Mac (there's just a limited Microsoft Messenger for Mac), while Yahoo has a very old Yahoo Messenger for Linux.
Google Talk uses an open protocol, XMPP, for instant messaging and Jingle, an extension of XMPP, for VoIP. While Yahoo Messenger and Windows Live Messenger are interoperable, the real basis of IM interoperability was put by Google Talk. There are also plans for AIM interoperability.
Chat in a browser
While there are services like Meebo, that allow you to use multiple IM networks from your browser, Google has implemented this for Google Talk in Gmail, treating IM conversations the same way as emails. Google also records the chat logs and makes them searchable in Gmail.
Google says: "Google Talk currently does not encrypt chats or calls. But we are working hard to make many improvements to Google Talk while it is in beta, and we plan to fully support encryption of chats and calls before our official release." Yahoo Messenger and Windows Live Messenger don't offer encryption.
Google Talk is included in Nokia 770 tablet, and can be used on a BlackBerry (Yahoo Messenger is also available).
You can argue that it has less features, but Google Talk setup has 1.45 MB, Yahoo Messenger has 9.5 MB and Windows Live Messenger has 15.3 MB. This is a good indicator for bloatedness.