You won't have a problem locating an Uber at 1:00 AM at IAD. May take 3-4 minutes instead of 2-3, but that's it. The fare estimator is pretty accurate and if you add 20% for a tip, you are still at $36.

For what it's worth, an UberX will likely run just over half of a taxi, so it's about as good a deal as you will come by to Tysons.