These training collars are amazing—the best set I've ever had. They hold a charge for a very long time, are easy to recharge, have good indicators, and offer great range. My dogs respond well to the tone stimulus, and I rarely have to use the other modes.
My only issue with this system is the collars themselves. While they're made of nice materials, they're hard to adjust, lack a ring to attach a temporary lead if needed, and are made of materials that aren't very high grade.