What I like about this light:
Quality build, if you thought the X5 was built like tank, you will really like the XO.
Long throw for a 1 watt light, nice and white with good side spill.
Good run time of 3+ hours at full power.
Lens and tail switch built like a tank and they work. (XM-2 take note)
Feels real good in your hand.
What I do not like:
The XO seems to be over built, making it larger than it needs to be IMHO.
Overall I like this light better than my:
ARC LSH, X5, KL1 on E2E, XM-2.