Back in AutoCAD R12, R13, and R14 there was a bug that was not bad, a bug with benefits. The bug allowed you to speed up the plot regen by over 200 percent faster making the plot preview and plotting much faster. All you had to do what hit the keyboard spacebar while the plot was regenerating and BAM it sped up to light speed. Several years back when I was on the AutoCAD Team I discussed this good old bug with a veteran AutoCAD developer and why it might have occurred and got into a fascinatingly long geek discussion about evaluating fiber switching etc.
Today you no longer plot regen or have the ability to speed up plotting by hitting the space bar but things are faster these days and technology has changed dramatically but I will never forget walking up to a coworker when they were sitting there at the plot regen dialog and hitting their space bar and the regen speeding up and their look of amazement.
So not all bugs are bad as some have nice hidden side effects.