I have one (better beamer) and recommend it. It works great for fill flash on bright days. I have had mixed results in dark wooded area's where extra light is needed. I think it works best on birds, especially birds in flight. It is effective out to a 100 feet. I've tried it on deer and other mammals, but it's hard to make the harsh light look nice.
I do have one HUGE warning though. Never forget to remove the magnifying lens (it uses velcro) or cover it after taking the picture. It will burn holes in your flash gun, camera or worse catch your vehicle on fire. And it does it surprisingly fast. I have three melted spots on my flash gun to prove it. I'm sure you remember from your younger days what happens when you use a magnifying glass in the sun.