Bin's are going to vary. Most people have reported getting R bins and some Q bins. At this price, you are going to get whatever they put in them. They work fine on AAA rechargeables and should work fine with lithium AAA's.
As far as water resistance, it should be ok. It might leak around the lens. For $20, I wouldn't expect it to be more than water resistant. It's a great light for the money.
I did wonder if a Pila 150A would fit.
You can find more info from the LED Museum:
http://ledmuseum.candlepower.us/fourth/metalg.htm