Highlander Pickups are favored by lots of pro players, including Woody Mann, Martin Simpson, David Crosby, Graham Nash, Bob Brozman and others. The biggest attraction of Highlander pickups is their fat, complex tone. The tone of all undersaddle pickups is a bit stringy by definition, but the thick, coaxial design of the Highlander gives it the ability to sense the entire movement of the bridge, giving you a pleasing blend of body and string that is unlike any other undersaddle. This same design also makes these a great match for resonator guitars, and Highlander is the pickup of choice for anyone playing a National or Dobro.
One caveat about installing Highlander pickups in your guitar: All undersaddle pickups sit in the bottom of your guitar's saddle groove, and they typically run some sort of thin pilot wire to the preamp inside the guitar. Most modern undersaddles can be installed without any modification to your bridge or saddle. But Highlander's slightly thicker pickup element means that you may need to rout the bottom of your bridge to fit the pickup under the saddle. The current design of this pickup is more slender than the rope-ish Highlanders of old, but I still think the pickup benefits from a modified saddle groove.