They're not terribly tight and in fact I wore them for the first time on my 40 mile ride Saturday. I found them to be comfortable overall and I like the bibs better than shorts. My PIs seems to be made of material that simply stretches a LOT more than other shorts I have including the Falconi. I'm 6-1 236 pounds and tyipcally wear 38" Levis (snug) to give you a data point.
My waist is somewhere between 36 and 38, and while the XLs I got are snugger than I had anticipated, that hasn't proven to be a problem. They're easy to get on and off, there've been no bursting seams, etc., and I've come to appreciate the fit - no moving or shifting around, and they offer at least the illusion of greater muscle support, if not the real thing.
I'd say the Falconi bibs run true to the size chart that's on their website. If you're close to the large end for a particular size, the bibs will fit snugly. If you don't like snug, consider ordering the next larger size.