The KL3 is a very useful part of an emergency light set in my opinion. It provides reasonable run light output for a long time.
With a 3-cell (123) light is provides 7 hours of close to 20 lumens. It's not a too-tight spot, either.
It's a well-designed, pushed 1W Luxeon light in a large package (as compared to the Arc at the other end of the scale).
I fell into a sale a year or so ago where I got three 9Ps for $40 each. In my emergency lighting bag, I have all three. One with an SRTH turbo head, one with the standard P90, and the last with the KL-3. I also have the two spare front bezels and a spare P90 and two P91s to open up my options (as well as a spare N2 for the turbo head).
The 7-hour run time in a 3-cell light makes the KL3 very attractive.
It puts out a bit more light but at a huge size cost as compared with the KL1. MY KL1 is more purple than my KL3 (and the KL1 is newer).
However, both the KL1 and the KL3 PALE next to the KL4 on the L4 Lumamax!!!
Cheers,
Richard