Location, location, location! You're able to be close to Bairro Alto, but not hear any of the noise. My friends and I stayed there during one of the busiest nights of year (St. Anthony Eve), and slept great throughout the night. My favorite room of the apartment was the living room. It's a great place to unwind with friends, play some music, enjoy the exceptional views, and take a great nap! We never used the AC because I didn't notice it until the morning we left, but following Alex's recommendations keeps the apartment cool. Be aware that the bathroom has a slanted ceiling that's not made for the 6'4''. Also the hot water requires a little patience and ingenuity, but it's there! Alex is a phenomenal host with great communication and quick fixes for anything you need!
Side note - the tapas restaurant next door was fantastic!