I like mine a lot. It's the light I normally pick up if I need a light beyond my EDCs for something. It's pretty bright, white, reliable (good tactical switch), has a good, wide hotspot and lots of spill, runs about 2.5 hrs on 2000 mah nimh's (about 1.5 hrs on alkalines, I'm told). It put's out more light than my Q3 (mostly in the form of a wider hotspot) and runs for basically no cost on nimhs. Other people have claimed their Q3's are brighter (Luxeon lottery?).
It is easy to disassemble if you want to change something, and has been perfectly reliable so far. It has very thick walls which some don't like because of their weight and others like for their apparent strength.
Criticisms have been that it doesn't drive the LED at a full 3W (most 3 W'ers don't) and has adequate but not bulletproof heat sinking. If you wanted to drive the LED harder, you might want to upgrade the heatsinking.
Some other 2AA lights look comparable, although I don't have any of them. Emilion's 3W 2AA light runs shorter but may be brighter, and is certainly cheaper. This
Nuwai is only a 1 W 2AA, but the 1xCR123 version I have puts out a nice beam and it's a deal at $21.50. Tactical clicky too.
I think you can't go wrong with the XM3.