Has anyone tried sims xtreme limb saver system, or PSE NV system dampeners? If so, could you let me know if they work. Thanks a bunch.

I have not used the former but have used the latter. They do work well...at least as well as the original limbsavers however they are difficult to install as you need a full sized bow press to do it.

I have heard nothing but good things
I am putting them on my new bow.
Search this site, there have been other threads on the topic.

I'm shooting the PSE NV system on a bow currently and have noticed a difference in the vibration.
However they do add some weight to you bow and like PA said, you'll need a bow press to install.