Stayed here a week ago Friday. Shuttle from airport was right on time and we were first in line to checkin. Check in was painless, and the clerk gave us b'fast vouchers since "it was our first time at an Aloft", which was very nice. He also confirmed the shuttle wouldn't take us anywhere but the airport, but that we should ask the morning desk clerk for directions to the Millbrae BART station.
B'fast was good, decent menu to order items from, and the morning desk clerk gave us easy to follow walking directions to the BART station. About a 12-15 minute walk on paved sidewalks with one big street to cross (with a crosswalk and lights). Saved $4-5/person on BART fare by not getting on at the airport stop.