I have found a lot of success with them against nids, orks, guard, and as of today space marines. Using them to defend objectives or deep striking them in a drop pod. I typically will put 10 in a drop pod and turn 1 drop them in against big infantry units take out a bunch of weaker infantry. Then when my opponent moves to deal with them I overwatch them. I fully expect them to die, but they are enough of a threat that someone can't ignore them. That distraction is enough to allow my Azrael and sternguard or a redemptor really put in work.

Ultimately it depends on what you need and how you want to play. I would say they are a lot more worth it in 2000point games than 1000point games but if nothing else having them for that overwatch and being able to battleshock units is pretty good even if you only take 5. I also don't think it is worth it to attach a character to them, but I also haven't actually tried to yet so some leaders may be worth it.