Just got my Ventum One last week and built it over the weekend. Due to work schedule this week, I only got 3 rides in so far. This is our second Ventum One in the family (my wife bought hers last year).
From the testing done by Slowtwitch members, it's not the most aerodynamic bike (although it's not far off...), but to me, the biggest benefit is the comfort and stiffness. Broken/rough pavement is not a problem at all. Somehow it manages to isolate you from the crappy road without loosing road feel. As to stiffness, I used to be a sprinter when I was younger and can still crank out some peak power. The Ventum doesn't flex, so everything just propels you forward. Prior to this, I have a BMC TM01, which is a pretty darn good frame. On the roads I ride, I commonly had to sit up on rough pavement as it just beat the heck out of me, not so with the Ventum.
Another aspect that's important to me, it's very easy to work on and our preferred Campy EPS fits without any problems what so ever. Battery nicely tucked in the frame, the charge port right behind the stem and easily accessible, all connectors fit through the frame without needing to modify.
In terms of handling, it feels like riding my road bike (Pinarello F8 if that matters). Handling is quick, but not twitchy. For descends, the Ventum tracks really nicely and you can sweep through corners with confidence.
All in all, so far I really love this bike.
"Suddenly the thought struck me. My floor is someone elses ceiling"-Nils Ferlin