Ah! So it's called column select. Oops!
I am trying Alt+Left Mouse in Windows XP but it doesn't seem to work. Is it different under Windows?
Column selection interacts nicely with multiple selections, too: Use Ctrl+Drag (Command+Drag on OSX) to add selections, and Alt+Drag to subtract selections.
I am thinking about buying it to use under OSX. The XCode editor is not my favourite to put it lightly.
Keep up great work!