I've been trying to wrap my head around this issue of quick switching times not being obtained...
It has been pointed out that I need super-low gate resistance fets.
fair enough, but I don't think the resistance is the problem, cause the close-to perfect square wave from the PWM pins is deformed when I connect it to the gate.
The AVR simply don't have the juice to charge the gate field fast enough.
Reducing gate resistance, I think, would just lead to a more distorted pulse shape, as the output current from the AVR I/O is not going to increase.
Using logic level hexfets would increase the gate capasitance whit roughly 33% and further deform my gate signal.
I think I'd better throw in a few more small transistors to drive the FETS properly instead of expecting the AVR to do all that work...

All in all, this doesn't seem to turn out as simple and straightforward as I expected...