I cast a 9'0" 5 wt. One when they first came out in the Summer of 2010. I cast it side-by-side with my Sage Z-Axis and, in the end, I kept the Z-Axis and let the One go. I think I posted a short review on the One back at that time.
Last Winter for a project, I built a Sage One 6 wt.; for heavier streamer fishing and when the wind picks up. It's a very nice blank.
I, too, just joined Trout Unlimited as a Life Member and I'm waiting for the delivery of the 9'0" 4 piece 5 wt. One and the Sage reel that they're putting together with it (they say it takes about 4-6 weeks to get the gear). Frankly, as you know, the retail value of the gear is almost the cost of the Lifetime membership.
As Larry has said, the Helios is also a very good rod and I don't think that there will be anything about the Sage One that will make you want to retire you Helios. And, of course, you still need a back-up rod; for whichever one becomes your favorite........................