I myself took a direct eyewall hit from hurricane Andrew. That was no joke. Building code back then was not a good as it is now. Roofs should hold better now. Irma is forecast to enter FL as a Cat 4. That will be a little weaker than Andrew so that's better than 185 mph though still pretty bad. Landfall in Fl at it's current 185 mph wind speeds, well I couldn't even guess at how bad that could be.
A hit from a storm such as this is such a destructive event it's hard to describe. EVERYTHING gets damaged or blown away. Fences, sheds, screen enclosures, cars, vegetation, utility poles, street lights and signs. Streets become blocked from tree limbs. I find the aftermath worse than the actual impact, it lasts much longer.