I have decided that the only people who will honestly say "Piledriver sucks" are either sworn enemies of the deck and want people to play sub-optimal lists or are people who understand that the deck is able to do the card-advantage thing but don't realise how it works in practice. I know when I was new to the deck I thought 2 Drivers was all you needed. Getting in lots of reps taught me that even 3 is not enough.

http://mtgtop8.com/event?e=13386&d=278496&f=LE 4x Goblin Piledriver was pretty good for me on this day... and literally every other time I've sleeved up Goblins. Whatever, do what you will but if you're new to the deck, just try out 4 Drivers and wait till you slam 3 of them out of nowhere with a haste lord out.