British GM Joe Gallagher is one of the top experts on the KID and has written a great introduction to it for Everyman Chess called Starting Out: the King's Indian. I highly recommend this entire series. Very nice balance of specific lines and general explanation by someone who really knows. He devotes about 20 pages to the 4 pawns attack. (He also has a nice chapter on the Saemish if you decide to go back to it).
King's Indian Defence (Four Pawns attack)
thanks for the advice, MrZugzwang, do you play the opening yourself as white?
Is there anyone else who does?

I play it as white but never against stronger players. Against weaker players it can be a great weapon. (I played against it as Black back in my OTB days and was summarily blown off the board more than once) Against stronger players I'll either play the Classical line or the Exchange.
if you play it as White be sure you are prepared for the newer variations with 6..Na6 (instead of 6...c5) with the idea of 7 ...e5.
do you think the four pawns attack is unsound?
Do you think that it would work for surprise value against much stronger players, given its agressive nature?

I don't think the 4 pawns attack is unsound at all : it's just not very popular among professional players.
As for the surprise value, I think it's low, as the attack is very popular at class level and every seasoned KID player will have some experience fighting it. However, it doesn't mean you cannot beat them !
Hi. I have had some bad experiences with the Saemisch variation of the KID and would like to take up the white side of the Four Pawns Attack. Does anyone have any experience/recommendations/suggestions for it?