In v0.7.5 Scaling is broken. (OS X version checked)
1) % scaling does not work properly. You cannot change the scale in % greater than 100%, but you can change the dimensions and the % reflect that change.
2) If the item is scaled bigger than the platform, once the red border shows, FS stops responding to basic commands in Slic3r. Only way out is to Quit and start again. This error does not show in Cura, did not check Cura2.