A Bug's Life

That glass etch spray is pretty awful - the previous owners of our house sprayed it on the perspex panels in the front door, and left a dribbly mess behind that we've no hope of ever being able to remove (spraying onto glass, as you point out, is rather easier to remove). This is probably more a product of their woeful abilities in the arena of DIY (I don't have the full hour required to catalogue their efforts), but it does seem to be remarkably difficult to get an even, drip-, run- and cat-hair-free finish.

The window film seems like a much, much better idea.