We've just pushed an update that fixes:
- Deleting group-layers in Sketch-view
- Incorrect pixel-density in new images
- Brush-scaling on the canvas (Shift+drag) required too much motion
- Awkward slider-controls in Sketch-view
We're also curious as to whether the pixel-density fix might improve the lag which some users have experienced, we'd love to know if this is the case! :D