kim, i've never scraped the sides. the under belly of the lip spoiler, yes i have
(but who hasn't
) if you scrape underneath, don't worry. it sounds bad but you can't see it!
no problems with curbs yet. if you have to go over a speed bump of up a steep curve (and i mean steep), then angle the car.
another tip, just remember that if you add the lip, the concrete parking slabs may not fit under the nose of your car. basically don't judge how close you should be to the slab by looking at the car beside you.