I used this method after I bought my first ascenders. I had two handled ascenders and knew nothing about climbing systems, so I put a footloop on each one and started climbing. I didn't know this was a bad idea until the good folks of Cavechat let me know that this was dangerous and "the least efficient method" of climbing. Now I'm starting to question some of the judgements of the Jumar system, especially after reading the Ascent chapter of Vertical.
On Rope calls the Jumar method unsafe since letting go of the ascenders will leave the climber hanging upside down, and that there is no easy way to rest while climbing. Why the obvious solution (adding safety slings) is not mentioned, I don't know. Ascent also tells us that the Jumar system has no "resting position" which may mean that there is no resting position as part of the natural climbing cycle. Further, Ascent says that the Jumar system has poor safety (why?) and "copes poorly with all maneuvers." This last bit is certainly rubbish. It may not be the best on bad lips, but I can downclimb, pass rebelays, and changeover far faster and easier with Jumar than with Frog. This may be because I Jumar without a chest harness. On Rope and Ascent call for the footloops to pass through a carabiner at the chest. I never considered trying this since I had no trouble staying upright.
One complaint is true. It is tiring. Compared to frogging. Originally, when I didn't know that frogging existed, I thought Jumaring was easy. I've used it with no significant fatigue on pits of 15' to 90'. Obviously, for long climbs and weak arms, another system is better. I think more people should consider Jumaring as an option. If you have short drops, what beats it? Forget the chest harness, all you need are two ascenders, two footloops and two tethers. In one cave with a couple of extremely short pits I even skipped the tethers and seat harness. The only systems with less materials are what? Prusik loops? It goes on and off rope very quickly, climbs pretty fast, and the cycles (for me) are longer than frog cycles.
Thoughts?