I've had a KL4/L4 for almost a week, now...Notes:
1. The Luxeon technology is still hit and miss when it comes to beam color. One of my KL4's is super white. The other is a pea green. I've heard this isn't an isolated incident.
2. This little light heats up faster than any incandescent. It will get too hot to touch.
3. The instant on of an LED is awsome.
4. The clickie switch is brilliant. Lots of pressure for the click, perfect pressure for quick on/off functions.
5. The street price fopr just the KL-4 LED hread is 90-100 bucks. Better off buying the complete Lumamx L4 light, instead of the seperate pieces.
6. Light output isn't necessarily greater than a SF E-series, but the beam quality and color is different than a Tungsten bulb.
--dan