Anyone have any experience with them? If so, are they worth the money and will it cycle sub sonic ammo?

They are great. They do work better and more quietly than standard buffer spring set. I have them in all my AR's, especially the AR10's.

I don't own one, but a good friend does. He runs them in all his AR's but had problems with it in his 10 inch barrel 300Blackout that was suppressed running subs. He had the buy the spring kit, 3 different springs, and test it until he got the preferred results, which he did. It now cycles and runs fine. I do like how quiet it is, but won't spend the money myself.

I run one on a couple guns. 8" blackout with subs no problem.
You might have a gap between the buffer and your BCG. This will cause issues as the JP unit is designed to be in contact with the BCG. Shake the rifle and listen for a noise between the JP spring and your BCG. If there's a noise you might need to put a spacer in between the spring and the end of your buffer tube.

Have one on my 6.5 CM. Like it. Quiet.

Just put one in my .300 BO but haven't had the chance to get to the range yet.

super smooth and quiet
Really evident when shooting suppressed