Beijing to Harbin should only take you about 1.5 hours, not 2.5 hours.

If you fly from PEK, Beijing Int'l Airport, I would suggest Air China rather than China Southern. Air China fly this route with new B737 and/or A320, and China Southern do it on old MD82/90.

The first main difference b/w F and Y in China, is the waiting area - you will get lounge access in PEK, not much fancy stuff, but quiet. But do not expect priority boarding, the ground staff never understood how to arrange that. When you arrive at the queue, just ignore them, walk straight to the front and wave your F boarding pass to the gate staff, they will let you get onboard first.

Second difference is the service, as many already said. On a 737/320, you will get the cabin supervisor and one dedicated staff serving 8 F passengers, comparing to 3/4 serving the rest 150/160 passengers.

To me (not for everyone), the third plus point is the food. Food in F is eatable, and I will ignore anything served in Y.

There is a special airline China United Airlines (in old days below to the army), now part of Shanghai Airlines Co., fly from Beijing Nanyuan Airport (still a army base) to Harbin once a day. If you stay in a hotel towards south or west of the city, I would recommend that - you will avoid all the traffic to PEK.

They only have Premium Economy class, with larger seat but Y class food. But if you fancy something special, that airport is very interesting.

Finally, Chinese F class is only 50% more expensive than a normal Y fare. So I would recommend it to anyone travel to China. I normally do about 60 domestic flights in China every year, only do Y class if F seats all been sold out (on certain routes, they are so popular!). My employer changed direction this year, I probably only will have 20 domestic flights in China this year, not enough miles for my China Eastern and *A cards.

Enjoy your trip!