Better yet, it could toggle between "the rather small default size" and "takes up 3/4 of the area". Don't really mind if it's a doubleclick or a keypress (is F1 used for anything...?), just would be cool if we kept such a function somehow.
The reason why I liked the broken behaviour so much is that usually the log pane is best kept small, because it's really not so useful. You mostly want to see the editor, and maybe a few one-liners that the compiler spits out. The default size is just about good for that.
Occasionally though, you get STL errors which output 30-35 lines of text, so you have to resize the log pane to be able to figure out where they start and where they end. After that, you wish that the log pane could just disappear again, because now it takes 3/4 of your screen. F2-F2 was a nice way of doing this fast and consistently.
Now of course if you could just hit a button to make the logpane pop to "full size" and back again, you'd not even have to touch the mouse, and you'd not need to try to hit that narrow resize margin. That would be really cool.