Man its so frustrating, when you have a unit almost produced, that can be cancelled in under a second by a miss-press or lag.
I would like a confirmation button added, that you wish to cancel the building of a unit. I know it may slow it up a bit, but think of the turn mistakes you'll save
Or even a undo type button
E.G. Catapult is
1 turn away from being produced, so you click the unit line, to see what to build next (you know..plan), an nothing happens. So you press again....
WTF?!?. I didnt want to cancel my catapult which is almost built, for a friggin skirmisher
maybe an "undo last move" button is called for at least? I dont know how many times ive moved an archer and thought "crap, why didnt i attack with him before i moved!?"..... *restart map*. I see carrots point on patience but like the op said, sometimes lag or a fat finger can mess up your whole day 
