While drawing i flip the image from time to time to see if the proportions/anatomie/... are ok.
In Photoshop i choose: Image -> Image Rotation ->Flip canvas horizontal
How can i do this in Illustrator?
Select all (apple a) > Object > Transform > Flip Horizontal
Not that you need two ways to do this, but it's something I do frequently and use the hotkeys/tool key.
Press "O" (to select flip tool).
Hold shift (to maintain proportion), drag in the direction you want to flip, blamo yer done.
it's pretty dumb there's no "real" option.
Make sure all your objects are unlocked too, Fritte.