+1. They budget for these things and usually it's one of, if not the last, steps in the hiring process. Almost every time I've flown out for an interview, the offer came soon thereafter. They wouldn't be spending money on you if they didn't think there was a good shot at a fit, so as others have said, RELAX. Be at ease - they obviously are serious enough to spend maybe $1k on getting you out and back (hotel, flight, time with personnel in the office, etc.) so while you may not have it totally in the bag, I'd say if you don't fuck it up, you're almost there :) Just come prepared, know your shit, and you'll do fine!
Premature though it is, CONGRATS ON THE NEW JOB! :)
Premature though it is, CONGRATS ON THE NEW JOB! :)