Selection as it works now selects several strokes (which are completely within the selected region) and then displays a rectangular box for shifting and scaling purposes. However, it is not always clear which strokes are selected. Especially with the lasso tool, one can easily exclude a stroke which remains completely within the displayed selection area.
I'd propose to somehow highlight the actually selected strokes. For example by some sort of neon effect. E.g. paint the selected strokes with a lighter and thicker pen or highlighter before drawing them in their normal form. A fancier and more elaborate version would be to have them flashing or oscillating like the power-light in standby mode on some laptops.