If it's my choice, I always work in Sonar. But I have worked in ProTools, Ableton, and even Sony Vegas (for a mix job, which was painful) when it's been required. I'll have a crack at anything.
I think DAWs are like mixing desks in this regard. It used to be very hard to work professionally if you could only use one desk. Now it's hard to work professionally if you only use one DAW. ProTools will come up a lot, but other things also come up.
Bottom line: be an audio engineer, not a guy who knows program X. If you understand engineering and audio fundamentals, and you're got decent computer literacy, you can work out any DAW fairly quickly.