I always fill my tires to 10% under the maximum listed on the sidewall which allows for a modest increase when driven and/or in summer. I don't mind the slightly harsher ride, and it helps with handling feel and mileage as others have stated. Other than slightly rougher ride and "maybe" reduced puncture resistance, there aren't many downsides as long as you are in the rated range of the tire.
On bigger, heavier vehicles, with all other tire specs being equal, I seriously evaluate tires that have a higher psi rating. One, it's a heavier duty tire and should suffer less degradation, and two, the extra additional psi can be used in tuning the handling better when the vehicle is heavily loaded, which can sometimes result in bulging sidewalls and a ride that wallows.