There was another thread about Jajuan Johnson a month ago in which I professed my love for him, and that hasn't changed (although Jeremy Tyler's leaping abilities despite his pudgy frame make me want him too.)
I'm a Michigan fan primarily, but that means I watch other Big 10 teams as well, and I've seen him play a fair bit. In college he was a good rebounder. He added range to his jump shot in his senior year, which moved him outside a little more than his earlier seasons, but when he was a sophomore he was almost solely a post player, and he was a decent at it. There's certainly the possibility that he can fall in love with the jumper, like many a big man in the past, but I wouldn't consider that a given.
The rebounding concern I think is less based on college stats (as mentioned, they were about 9 per game, and that was in the big 10 which tends to have slower offenses and fewer possessions/rebound opportunities) and more on his thin frame. In college, where he was often matched up against smaller/less athletic players, this wasn't a problem. But his athleticism isn't off the charts, and he isn't big, so that might cost him battling for rebounds against larger/more athletic competition.
Still, he's a hard worker, a good defender (more blocks than fouls last year) and is definitely the most NBA-ready player who might be available when we draft. If we want someone able to give us 15-20 good minutes off the bench this year, then we absolutely pick Johnson. He will never be a star, but we're talking the 25th pick in a weak draft year.