he is being successful because he keeps the batsmen surprised with delivering the ball of wrong foot.
Speed: basically 78-84 MPH, not bad can always get better.
LnL: Slightly outside Right handed's off stump, angles across batsmen, length is quite correct for new bowler, slightly short i think but batsmen have not be able to capitilze on (slightly)shortness of bowling coz right now they are trying to figure out his action too much....and are preoccupied with that....
Variety: Not much from what i saw, doonoo if he uses Slow ball or changes length very often....when he went around the wicket in game against SL...surprised batsmen a bit but i think will be lollypop bowler from around the wicket for batsmen as soon as they get over his action...and wait for him to pitch the ball up in attempt to get batsmen out as that will be the only way for him to geta wicket as by bowling around the wicket, with his action, it will bevery hard(nearly impossible) for him to get the ball to move across the batsmen.
What he needs: needs to develop in-Cutter like Pathan and Vaas....obviously needs to learn reverse swing, but with his action, i dont see him being able to generate reverse........BUT on bright side, if he does get any amount of reverse...that will be lethal....even more than Shoaib akhter's...coz his action is just way too strange one to expect reverse from.
If he helps Pak to T20, i ll be glad....but do not expect this guy in Pak, reversing the ball, gaining pace or developing in cutters like wasim or even Irfan...thats just the reality but i will be glad if he proves me wrong