I'm based in DCA and fly this trip quite often. I've never had it cancel, but we have had several delays that were exacerbated by the fact that the mechanics, planes, and crews aren't interchangeable. THIS is one major thing that will get fixed once UCH negotiates a Joint contract with the pilots and mechanics. I completely understand the passengers frustration when you are sitting at a FORTRESS HUB of the airline whose ticket you hold, yet there is only ONE plane, crew, and maintenance team to support your flight! Talk about a shallow bench...
When they get in a bind, they will ask for the employees to 'take one for the team' and bail them out. This involves waiving the contract. Some will do it, but I will NOT. On a recent fligth we had an engine air bleed problem and had to return to the gate. Since there we ZERO mechanics at EWR that could run the engine on a 767 300 they asked the pilots to do a maintenance troubleshooting engine run -- I opted to not bail them out. Again, a contract negotiated in good faith will solve all of these problems. I will do this very same flight a couple of more times at the end of Oct and mid Nov. They will once again roll the dice and hope nothing goes wrong with the plane that requires me to waive my contract....
FWIW, a large and growing segment of the UAL pilots are coming around to the same 'place' that I'm in. We are watching our flying erode while CAL is growing. After 31Dec11, UCH will be free to park UA planes, close UA pilot domicles, and furlough UA pilots. Will they really do it? I know it doesn't make sense to do any of those things, but my experience this past decades shows that they will ALWAYS take the route most painful to the pilots. There is a very real possibility of UA parking 757s (up to 30) in the coming year. Is it any surprise that I'm not interested in 'taking one for the team'??

Sorry for a bit of a rant, but I wanted to be realistic about what anyone will face when trying to fly on these 'cross fleet' routes.

FWIW, I'm not punishing, or doing anything to target the passengers -- what I'm doing is protecting my career (cough, cough, gacckkkk...)