I spend most of my time on AirTran and Delta with an occasional ride on Northworst and American.
AirTran is usually slightly cheaper and their web site is easy to use. They also have smaller change fees. But the check-in lines can be very long and the kiosk doesn't always work so I can bypass them.
Delta has high change fees and a crappy web site. Their first layer of customer service must be based overseas cause they sure don't speak english.
If your flying Northwest you may want to consider taking a portable breathalyzer. So you can test the flight crew before you board.
I got on a commuter some years ago and while waiting to depart the gate I look out the window and what did I see? A strip of duct tape on the engine cowl. Doesn't exactly inspire confidence.
I arrived in Boston late one night just in time to find out my flight to Nantucket had canceled. I go to the info desk to find out my options. I politely inform the lady behind the counter that I really needed to get to Nantucket tonight and are there any other flights? . She says : "No I'm afraid not but that's not a problem sir. I'm already printing you out a ground transportation voucher".
"A ground transportation voucher?" I asked.
She says : "Yes sir, we'll pay for your ground transportation to get you to Nantucket tonight."
I ask : "Miss, do you know where Nantucket is?"
Never looking up from her computer she replies: "Oh yes sir."
After a long pause I says: Lady, Nantucket is on a GD island for chrissakes! What are going to do, get me a taxi with a snorkel?"
Needles to say I spent the night in Boston.