I really wish they gave any indication of what the stat altered in the game. In Fallout 1 and 2 I could at least count on it rolling me up some beneficial random encounters but in Fallout 3 it seemed to merely affect crit / to-hit calculations.
^ Not sure, but I would assume so. I won an BJ 19/20 times or so with luck 10, but I haven't tried with low-luck characters. I've assumed that the success is due to high luck.
@Anarchosyn: You get a few luck-based conversation options in NV. Otherwise, it adds to all skills a bit, and modifies crit. chance.
My new character won 32k on the slot machine and got kicked out of Ghamorah he has a 10 luck and it said you're feeling lucky at the top right. So it does but I haven't tried to find out how often it does as I wish to keep playing in Casino's (purposfully losing and then winning ... I do lose 1000 win 3000 from every casino just to keep them off my ass when I want some quick cash.
I got kicked out of two Casino's after "beating" their slot machines with a character that only had mediocre luck (5). Granted it took me about 40 minutes to do so...