Absolutely beautiful piece of functional furniture. I use this rower 3-5 times per week. The display is a little awkward and not nearly as advanced as the competition but for anyone short of a pro, it provides all the basic functions you could want. I've used plenty of rowers in gyms but this was my first purchase for home use. It was an excellent alternative to running outdoors in the winter and as an alternative to running when the legs need a little more recovery time. I have it set in the middle of it's resistance range and it is still plenty challenging. So there is a ton of adjustability in that regard. It's not quickly changed but for a single user device this doesn't matter. It's a different feeling than an air fan but I really like it.
On theme with C2’s interchangeability, models D or E are essentially the same machine. When we talk about one we’re talking about both. The Concept 2 E is just 8 pounds heavier but is made out of stronger stuff all around — what’s plastic on the model D is aluminium on the model E, and what’s aluminum on the model D is welded steel on the model E. The only noticeable variations are seat height and display position.
The Challenge AR has the capability to allow the rower to control and adjust the resistance from “Feather light” to “Olympic sprint” delivering a silky smooth resistance to the user’s effort and instantaneous response to input with no “flat sport”.  With water resistance being the most accurate manner in which to simulate actual outdoor rowing, the Challenge AR provides a smooth and consistent sensation throughout the range of motion of the exercise experience.  
In sweep or sweep-oar rowing, each rower has one oar, held with both hands. This is generally done in pairs, fours, and eights. In some regions of the world, each rower in a sweep boat is referred to either as port or starboard, depending on which side of the boat the rower's oar extends to. In other regions, the port side is referred to as stroke side, and the starboard side as bow side; this applies even if the stroke oarsman is rowing on bow side and/or the bow oarsman on stroke side.