Originally Posted by shdflyer

In my experience, there is no downside as a 1K or Platinum. I do this all the time. I book 20-30 award tickets a year, and use about 1/3 of them. When I cancel the others, taxes always come back. Never had an issue, though some people report having to watch tax refunds closely to make sure they credit properly.
As a 1K or Platinum, I always book one-ways unless on an international award where I want a stopover, which is only available on round trip tickets. One ways allow a lot more flexibility, especially on the "return" -- many times I've changed my date of return after starting the trip. With ones ways this is easy if award space is available. With round trip, not.