I've seen Haislip play dozens of times in the last few years, some of them in the arena. He's a good 4th big if you surround him with good rebounders and defenders, play some full-court offence to keep him going (he's amazingly quick changing ends, although notoriously slower running back) and know how to use him for spacing purposes in half-court sets. When he's playing with confidence, he's a very versatile and dynamic offensive player: he'll get shots in transition, he'll create off the bounce from the high post, he'll play the pick'n'pop perfectly, he'll cut through the lane from the weakside. Good signing for the minimum. As I said, think a poor man's David West or an athletic Glen Davis without the hustle or the focus.
Haislip was easily a top-10 PF in Europe if you analyze them from a NBA perspective. Very, very easily.