The main use I see for this feature would be centralization: combining on screen information that Firefox already provides through a world of extensions with mIRC's great functionality and capability. So, it is useful, but unfortunately, not practical for the amount of effort required. It is also not even feasible from a programming point of view without recreating mIRC from the ground up. Embedding certain "desktop" windows into Firefox might be another story though... that would be interesting.
