I used it probably 10 years ago with analog cameras and a capture card, and it worked ok.  Now I'm trying to use it with IP cams and it's simply not doing it very well compared to my NVR.  The NVR live view and recordings are smooth with no frames dropped, no lag, no stutter.

Zoneminder on the other hand is a slide show.  Since the cameras are streaming in h264, I don't think zoneminder is setup to handle that.

Unless I'm wrong.

Someone please tell me if I'm trying to do the impossible with using IP cams and Zoneminder.

As an IT guy I gave it a crack for my handful of cameras. Of all the various software packages I tried it was the absolute worst in terms of configuration and performance.
 

ETA:


What are the specs of the compute you are trying to run it on? I know on my box with a Q9550 and 8GB of RAM it was seriously struggling.

Its a amd 8350 with 16 gigs of ram in a linux container (LXC)

It's not bottoming out, the problems I'm having are configuration related, I'm almost sure.  Or perhaps I'm trying to do something ZM can't do yet (dealing with h264 streams)

I used it at home for several years at home. I has one USB camera and an Axis IP camera. I always hated getting the damn system set up, but once it was running it was solid. Were the forums of no help in configuring your cameras?

I finally stopped using Zoneminder at home when I got my hands on some ubiquiti IP cameras. Their Unifi Video camera controller app is pretty painless. We're still running zoneminder for the warehouse cameras though. The cameras are all Axis IP cameras and I've had no issues there. We are running 1.28. For the price you can't beat the features

 
Check that you have the newest codecs and zm is actually using them? h264 shouldn't be a problem in itself.