First off I would like to say that judgin from the screenshots of the leaked beta, I love the tabs and love the fact they have finally been implemented. I have not downloaded it myself since it is a beta not intended for the general public. But I would like to contribute my 2cents to the idea...
First off I would like to see the tabs close on double click AND closed by middle click.
Also the taskbar button should have an option for a static text something along the lines of "# of conversations" or simply "Conversations".
Also maybe the adding of rows when one row has an "x" number of contacts. It will make it look cleaner.
Anyways thats my contribution.. hope it helps.
Edit:
A feature to "Close all other tabs" would also be well recieved .. I think
Also a way to organize the tabs in the bar. Move them at will... For example I have convesations going with "x" "y" and "z" I would like to able to organize them any way i want to, "z" "X" and "y"... Get the picture?