For most applications, like Explorer Windows, Browsers, etc. the default automatic grouping of Taskbar buttons is really appropriate, avoids opening unnecessary additional windows, and keeps everything much more organized.
However, since I installed Windows 7, I've been annoyed by the fact that there are some applications which would benefit by staying ungrouped, even if the rest of the applications continue to follow the default "Always Combine" behavior.
For example, with this automatic grouping behavior, all Windows Live Messenger chat windows are also grouped (of course), but that means you have to click TWO times EVERY TIME you want to get to one specific chat window. (or similarly, to wait till the taskbar preview comes up and then click). Additionally, the taskbar button of lights up whenever there's a new message/feedback from any of the chat windows, but there´s no way to quickly know from which one of the open chat windows is this feedback coming.
It would be great to keep them separated, so that each has its own Taskbar button, while the rest of the Taskbar buttons would stay grouped.
The user would be able to specify which applications would ALWAYS remain ungrouped, with separate Taskbar buttons for each window, even when the "Always combine" option is enabled. All other applications should stay grouped. *See Image*
This allows fast access to each independent window of the application, as well as separate, detailed feedback from each one of them.