I've never had to leave it on the playfield very long, the glue comes off quickly. So, I'm not certain how long you'd be able to leave it on the playfield. As with any solvent, regardless of how 'mild' it is, or seems to be, you don't want to leave it on there any longer than you have to.
I also use it to remove adhesive from cabinets. I've had more than my fair share of container games where the guy packing the containers taped the heads down with that crap brown packaging tape that leaves residue all over the place. Also is good to remove old adhesive from ramps and decals before reapplying them etc.
