it's a very effective way to get stronger. it's also fairly safe, unlike campusing.
i believe udo neumann (sp?) who co authored "performace rock climbing" with dale goddard, is one of it's first proponents. at least that where i first heard about it.
the wall is fairly steep (at least 45 degrees) and symmetrical; that is, the holds on the right and left side of the board should be exactly the same. this is so that you can do the same set of moves with both sides of the body.
think of doing a boulder problem starting with the right hand, moving up and right a few moves then downclimbing. then, starting on the same holds do a mirror image of same problem starting with the left hand.
apparently the symmetry of movement is very important. (it has something to do with increasing connectivity of the neural pathways in the brain, or so i'm told by people smarter than me...)
a typical work out might be 5 different problems (done on both sides of the body)that work different muscle groups with 5 repetitions done in each set. it's a way to weight train by climbing.
we had built one that allowed us to make 4 or 5 moves before reaching the top. it was hard to find holds that were idental from both sides. we even made a buch from smooth hardwoods. the wall had t-nuts on 4" centers to fine-tune the hold placement.
it's a fairly intensive workout and it is training. it's not exactly fun (unless your idea of fun is training) but it does work well.
eric something-or-other (the climbing trainer from pa who was/is married to the playboy model) has a similar regime called "hitt-strips"(i think.) he suggests using a weight belt or something like that, which seemed to me like a good way to hurt yourself, but maybe not. i really don't know much about his thing.
i seem to remember there being an article in one of the rags (climbing, maybe) about it.