I've got purple remains and glue all over my windows. It's been a long, slow process. Tons of elbow grease. I've tried every chemical people recommend and none make it come off "easy." You still have to work a tiny area at a time.
If I charged myself going labor rates, I would have just replaced the hatch glass 2-3 times by now.
Goo Gone works as well as anything else (not very).
2004 Honda Civic Hybrid "Eeyore" @ 49 mpg
-MaxIMA, OBDIIC&C, IMAC&C, Lower grill block
RIP 2000 Insight, 40k miles @ 69.2 mpg
2000 Insight, AKA "The Basket Case" or "The Go Pod" @185k miles @ 63.5 mpg
-IMAC&C, OBDIIC&C, Scott's aero panel, grid charger, cheapo sound system