Interestingly enough, the PH now explicitly allows the DM to disallow a character if it is too powerful compared to the standard (if the total ability modifiers are higher than +8 before racial adjustments, pg 18 of the PH under "Method 3: Rolling Scores".Personally, I prefer the 4d6 rolling. Using a set point buy / standard array make it feel too cookie cutter for me. I like the RP that comes out of having large deviations in scores. But I also suggest, like it says in the book, setting some limits (mainly a lower). I still want the players to have fun, and rolling a bunch of extremely low scores can make a player disinterested in his or her character...