I keep reading the rules for Holocaust and they seem pretty good to me. I've noticed though most people don't use it or are totally against it. Is it not that good or is the risk of a PotW attack not worth the trade-off? What's your guys take on it?

I only use it if i know my guys are gonna get wiped out, but apart from that I try and refrain from using it as their is a chance my dudes are gonna get killed because of it.

I've used it once against necrons but it doesn't work that well against them, try using it on some weaker/swarm armies.

Well... considering its an extra attack on mostly the entire enemy squad its pretty good.
Considering that only the brother captain is the one who needs to have the template touch him, its pretty good.

I have 1 holocaust on my master, 2 on my terminators.

I use it very often as it might, might do damage, it's str 5 after all.

And the enemy doesn't have to be in cc either!

It's a really good idea that should be taken far more often in DH lists but...it costs too much.

When we're already fighting for points for more bodies in the list those 20 pts are almost a PAGK. I think it should be included for free in squads of 5 or more.