Who ever invented it is my nemesis today. Oh sure, it does the job, but what about un-doing the job? I am standing in my basement, leaning on the window ledge, holding a heat gun to the casements and moving along a centimeter at a time, so that I can eventually replace the cracked glass . . . if I get the old one out before dark, that is. Very slooooow. Very boring.
Of course, if I could get the sashes out of the casements and do the work on a table, that'd be nice too, but no luck there.