Believe it or not, there was significant improvement in lost luggage, consumer complaints and flight cancellations in 2009 - much of this the result of airlines having fewer flights to deal with. From the WSJ:

Of course, the challenge for airlines, the FAA and travelers will be whether flying will bog down again once traffic picks up with economic recovery. When travel was robust in 1999 and 2000, delays became rampant, customer service went into a tailspin, airfares shot higher and airlines became a target for outrage in Congress.

The Journal's Scott McCartney ranks airlines in various categories:

Cancelled flights
--Best: Continental
--Worst: US Airways

Complaints
--Best: Southwest
--Worst: Delta

On-time arrivals
--Best: Southwest
--Worst: American

Bumped fliers
--Best: JetBlue
--Worst: Alaska

Lost luggage
--Best: AirTran
--Worst: American

Here's the full chart.