I have used AA, UA, NW, CO, DL and US over the past year or two. NW by far for the most awards. Generally only one on the others, except maybe two on DL. I think they all tend to follow their rules, the only problem is knowing all the finer details of their rules. You can not read them anywhere, you call one agent and get one answer and call another one and get another. So I won't rate them on honesty, but I will rate them on Customer Friendliness and ease of earning/reedeming.

I think DL and NW take the cake on ease of earning. I have used 60,000 miles of award tickets (1 coach redeemed on NW and 1 F reedemed on DL) and have 25,000 left and never had flew a DL paid fare, nor did I ever have any points credited to them from other flights. ALL DL points came from AM EX, Dining for miles, car and/or hotel rental etc, but the lions share from the DL Am EX and Dash to the Gate type things. NW also runs many many promos which generally post as described. A few times I have had to call and they get it straightened out quickly.

I just started flying US last year, and they seem to either post and/or fix them very quickly. With 3 flights I have enough miles for a free ticket. I got a bump voucher also (which comes out of award availability) and it was very easy to use.

AA booked online for a friends trip, no problems.

UA, I flew it, my parents booked it, no problems I know of.

I love that NW does not charge any fees for booking up to almost departure (I think you can book up to 4 or maybe 6 hours before departure) on Award Tickets. HATE that DL and CO charge you up to a $75.00 adminstrative fee if you book 14 days or less. THAT could come very close to being dishonest, since it takes no more work to book an e-ticket for a flight 5 days or 1 day from now than it does to book one 30 days or more from now.

CO is always quick to say something like, oh, we have no standard availability how about EasyPass (or whatever they call it) for twice as many miles? That galls me!