I agree you can hammer out geometry quickly with CSG, but quickly in the modelling world usually results in issues ;) (unless you're a speed modeller, of course)
Two more options for cleaning meshes-
Hexagon 2 at Daz3D. It's a buggy fairly feature limited program, but the polygon reducer does work well, and it's dirt cheap. Also, you could bring your mesh into a modeller which supports quadrangulation. It won't fix bad geometry, but it might help to cut back on tris so you can fix things easier by hand.
Two more options for cleaning meshes-
Hexagon 2 at Daz3D. It's a buggy fairly feature limited program, but the polygon reducer does work well, and it's dirt cheap. Also, you could bring your mesh into a modeller which supports quadrangulation. It won't fix bad geometry, but it might help to cut back on tris so you can fix things easier by hand.