On cheaper jigsaws the foot will often not click to exactly 90 degrees, or you might not be holding the saw flat on the piece as you're sawing, I've seen that more than I'd care to admit to using my jigsaw.
A good jigsaw, and cutting slowly/improving your technique should correct that kind of problem.
Depending on the cut, a good bandsaw with a small blade can work wonders.
The sawmax just looks like a smallish replacement for a circular saw. Ie good for straightcuts only.
A jigsaw can make fine straightcuts with a decent sawboard, but its slower.