+Dropped it way more times than I can count, usually while closed and turned off but also while it was running, and while it was open (both running and not).
+Totally stood on it, putting my full weight on the closed lid many times.
+Left it running in my closed backpack for almost an hour (twice).
+Used it indoors and out during drizzle, snow, the height of summer and the low of winter, I even used it on a beach once.
And through all of the above I never had any problems. The only issue I have ever had was when I was carrying it about 6 ft. off the ground while open and running (brilliant I know) and I dropped it onto a tile-on-concrete floor. That time the hard drive crashed but everything was perfectly fine.
I don't know what kind of build quality Apple computers have but I'm going to guess that it can't be that much better.