Am considering putting in a different trigger for my varmint AR.  Any opinions on Jard, JP or Jewel?  

Single Stage:  The JP hammer & trigger set is superb.  Full adjustability and a superb feel.  Takeup is next to nothing and no perceptable overtravel.  I have built two rifles with this system and really enjoy both.  Trigger pull without modifying the JP springs is 2.75 lbs.

Two Stage:  I have builr one rifle with the Jewell trigger/hammer system.  A nice 2 stage setup.  Well defined first and second stages, both of which are adjustable.  I have mine set at 1.5 lbs for the first stage an additional .5 lbs to the break.

The JP design is really based on the stock trigger with high mechanical advantage on the sear faces which can lead to a "notchy" feel if the sear face or hammer notch differ in hardness or are just plain too soft.  After many thousands of rounds through the JP-equipped rifles, they are still working perfectly.

The Jewell system is more complex, but may actually be more reliable in the long term.

Ditto on the JP trigger. Mine still feels the same it did the day I installed it. I went with the full setup, yellow JP springs and speed hammer.

If you want a two-stage, RRA makes a good trigger for the money, but they're not adjustable. Jewels are top notch, and easily adjustable.