The resource improvements are very helpful early on. The durantium refinery gives +4 raw production which can kickstart your production base. Personally I NEVER build them but some people do and the Ai loves them. When i acquire a planet with them I tear them down and replace them. The promethion pleasure park can be helpful on a large empire if you need that planet to be happy. 

Thank you both. That fits what I seem to be observing. Pity, the resources are fun to discover. I can see where they would be beneficial in huge world if you have already placed the Solar Plant or Tech Capital. 

Surely the anti-matter building is unique enough to be useful. It benefits everything like a second capital?

Or you could play as the Thalans.  You get Hives, which is a Durantium Refinery without having to get the Durantium.  

The resource improvements were great when they introduced them but perhaps a little OP. As seems to be typical, they over-reacted to the shrieks of the power players and made them nearly useless. I am kidding about the power players part. I actually think it was changed due to a disagreement among the devs.

In it's original iteration, the Antimatter Plant gave you either a 4 or 5+ adjacency bonus to everything. Now I think it is +2 and nearly worthless.

The Promethium Pleasure Palace originally gave a +6 to base wealth and adjacency bonus to moral improvements. The wealth boost was probably an error but still made some sense and I really liked it.

Someone made a pretty nice mod that buffs them up. It can be found in the mod forum as Worthwhile Resource Improvements Mod.

It's great that the game can be changed if you don't like something, but at some point I hope they get the base game balanced to the point that mods will only deal with flavor and not playability.