I have 2. The first works great. The second I have to not screw the coil on too tight or it won't make contact. I only use them as a grab and go out and about device.
I have tried the .6, 1.0 and 1.5 clapton coils. I think I like the 1.0 best but all 3 are fine. Of course you get longer battery life (and less juice usage) with the higher ohm coils. You can also get longer battery life if you turn off the light (but the light is so cool).