Yeah, speed bumps are a huge problem. You never know if you'll hit your exhaust on them. You basically have to come to a complete stop before creeping over it. And hope for no scraping.
Driveways and turning into places also sucks. To fast and you hit the ground with your front end, and then exiting you'll smash the exhaust. It's ridiculous, my Civic is lowered probably 1.5 - 1.75 front and rear and it gets annoying. Leaving parking lots, you get those front tires over the downslope, then creep along, praying for no scraping, then the rear tires go over the edge - now you hope your front end doesn't smash into the road.
Please don't go too low.