I'm on my second Xar because they are very comfortable, well-ventilated, provide good coverage, and look good. It has some significant flaws, however, that will probably keep me from ordering another one.
They may be just a problem for me, but here they are:
It doesn't hold sweat well at all. The padded liner has a break in it along the forehead, and combined with the thin padding, creates a river of sweat that runs straight down my forehead into my sunglasses. Of all the helmets I've had, the Xar is the worst for this.
As other reviewers has mentioned, the Roc-loc retention system is fragile. Mine broke way too early in its life, and I'm not going to spend $40 to replace it. I'd rather put that money towards a new helmet.
The Troy Lee A1 is heavier (I feel like I'm wearing an Igloo), but feels like (subjective, I know) it would provide more protection in a crash and holds sweat better. The Catlike Leaf is my sleeper pick; light. well ventilated, super comfy, and holds sweat well.
All told, if it works for you, go for it, but I won't be getting another one.