They work very well. I believe the maximum limits are a 16' wall and 500# each. Double check this info, of course. One risk is going too far and having the wall topple over, away from the jacks.

One guy I have disassembled barns with will sometimes lash two wall jacks to two posts and slowly lower a heavy plate to the ground with just two people: an unconventional use.

Jim

The closer you look the more you see.
"Heavy timber framing is not a lost art" Fred Hodgson, 1909