I had a wall hammer as my first LPS coral, and it was a disaster. It developed brown jelly after a few weeks, but I managed to salvage a small piece. That piece eventually died about a year later.
The problem seems to be the coral's inability to heal after being cut or fragged. I was able to get the piece I saved to heal by treating it with revive and hydrogen peroxide, but only after cutting off the dead portion.
Given the high mortality rate of wall hammers, I'm hesitant to try one again. On the other hand, I've had a branching hammer for about 7 months now, and it's doing great.