They are seemingly easy to build, especially to those who have not built much stuff before (in reality, a box-shaped coop is not much of any more difficult to build, nor is it any much more expensive per square footage enclosed). Also they are "cute" in an oddball, chalet-style kind of way.
I think that about sums up all their virtues.
On the down side, they are a great waste of space, not at all chicken-friendly compared to box-shaped or hoop designs (very minimal usable floorspace), next to impossible to ensure adequate warmth and air quality during wintertime in cold-winter areas, and many A-frame designs are hard to ventilate adequately.
The walk-in size ones may have *something* to be said for them, but if you are considering a typical reach-in size A-frame, honestly there are a lot of other designs that will really serve the chickens much better and be just about as easy to build.
JMHO, good luck, have fun,
Pat