I watched a lot of 90's baseball and never thought of Jaha as a disappointment, more of an over achiever. He didn't make the majors until his late 20's and never had huge expectations. Would have been nice if he stayed healthy but out of his control. By the time he left for Oakland he was 33 and out of the Brewers plans.
I would consider his teammate Dave Nilsson more of a disappointment, expected more of him and when he finally reached his talent level he left the Brewers at 29.