Anyone have experience with shim kits? Specifically for a Ruger SBHH but really for any revolver. Does shimmying a trigger, hammer, and cylinder have any real performance benefits or just make it 'less loose'?

My experience is it makes the gun more consistent, both in trigger pull and hammer energy.

I have hammer and trigger shim kits in all of my Ruger single actions and the Redhawk. I hadn?t heard about kits for the cylinder except to deal with Cassel of excessive endshake

Randy the shim kits are great especially with Endshake. Two S&Ws were corrected and shoot much better. Velocity was much more consistent. Although the cylinder gap only affects the velocity, the groups sometimes can close up. Vertical stringing one of the more noticeable results.
On the hammer or trigger, (in an exaggerated ) example: a loose trigger may have you pulling to one side and might cause you pull you shots.
If a hammer is loose and rubbing one side, or hitting incorrect and at the last moment, being forced into place then the results will be the "bounce" that although will be minute, it will affect accuracy.
In all instances it is "Consistency" When all is trued and tuned up, results are better.

One place that is often overlooked is the shim on the bolt stop.
Maybe I should have just answered yes to your question.

Thank you both for the responses. I ordered a variety of shims for the trigger, hammer, and cylinder. As well as, an oversized cylinder pin. Didn't really need any of it but I just can't leave well enough alone...