Bowman's biggest problem are trades, He makes awful trade or sometimes really good trades, but the bad trades overshadows the good ones.
Bowman's best ability is scouting/draft, which I believe he's one of the best GMs in that category.
Pros
Drafting, Scouting Europeans, and FA pickups

Cons
Trading and resigning players

So is Bowman a good GM or Bad GM

When Bowman gets fired, I believe many teams would try to hire him as head of Scouting or as an Assistant GM