Unfortunately have never been on a "completely or near empty" flight. Closest I got to was the last flight of the night from BDL to MSP on a 717. Out of 110 seats there was probably 30 people total, give or take a couple on the flight. All local passengers besides one or two connecting to RST or FAR. F was full, C+ was 1/4 full and Y was basically completely open. Left late due to deicing but the flight was smooth, I had an entire row of C+ next to, behind, and in front of me, and FA's were more personable and generous with drinks/snacks. Even chatted with the lead FA for about 10 minutes. Definitely a nice change of pace from my usual "completely full" flights.