Started teaching a simpler version of this pose in my classes -- the one I tried in my classes is the baddha parsvakonasana -- locked side angle pose... This one -- the locked triangle -- is tougher in a manner of speaking since the legs are straight and that calls for more flexibility. The one I started in class, is less intensive, since for that you bend the knee, on the side you are bending. That means the pressure on both legs is a bit less than in this advanced one.
B.K.S.says that these poses -- standing challenging ones -- prepare one for advanced inversions also (balance is the trick and all such poses get you there pretty swiftly). And he suggests that you practice them intensely at least once a week.
I like standing poses simply because they are tougher for me, even than headstand. I am that air element -- upside down most times, and being grounded is next to impossible:) So, yes, I like standing poses simply because they ground me. The effect lasts the entire day if I focus on a few standing balancers...
You will find how to do this pose instructions easily enough on the net.
But what you need, apart from such instructions, is
- a regular practice in lunges .. that could mean regular sun salute also, with the crescent or horse gesture pose actually creating that muscular elasticity at the hips and saddle region.
- ability to balance when you tilt your face up. This is a rather tricky sense of balance that gets challenged.
- arm flexibility.
- strong legs (that comes from holding standing poses for long).