I personally found that when Keane had time on the ball, he fudged it up. Unless it was a penalty, he was good from the spot. Whether it be a shot, a pass or a decision. But when he didn't have the time to think, he was deadly. He had great off the ball movement in his younger days too, but then he thought himself as a bit of a number 10 and for me that is where he went wrong.
Keane had good instincts, once the time allowed him to think vs. react, he often fluffed it. But make no mistake, he was a very good striker and for a few years served Spurs very well.
Management/team setup also affected Keane, he needed to be highest up the pitch (so he wouldn't try to be a number 10) and he needed a through ball at feet or over the shoulder (best volley I've seen consistently)