Betting hard at the microstakes are crucial for success, thats for sure. However I think betsizing preflop is not as simple as 4xBB and one additional per limper. At the microstakes they may be, but Im a firm believer in varying your preflop raises. Also I think its okay to aim for 3.5x or 3x at somewhat higher stakes. But things should not be so rigid. Sometimes you want to raise say the potsize, sometimes more and sometimes less and a lot of various factors are to be considered. Generally speaking you should often raise bigger from the blinds than you would from the button. Position and stacksizes matter a lot so you shouldn't just pick a number and blindy follow it. Hell, sometimes (really not often though) it may even be correct to min-raise. Like everything else poker; very situational.