Pluses: Shaq is an above-average rebounder (on both ends), an above-average post defender, and an above-average post scorer and finisher. He's also a good passer, especially out of the post.
Negatives: He's a poor perimeter defender, who especially struggles with the pick-and-roll. He's got very little range on offense, and he's a poor free throw shooter. He's not all that durable. He's slow and not overly mobile. He's got a big ego that has caused chemistry issues with other teams.