RandalThor, thanks for the feedback anyway, even if I had hoped for a bit more detailed input on the system itself. If you prefer one-roll attack resolution, then the system probably is nothing for you.
We OTOH found the second roll for the critical not really an issue since a) it gets necessary only if an attack successfully delivers a critical - which should be the clear minority of the attacks - and b) rolling the dice and looking up a critical, without any math involved, is IMO not prolonging combat resolution in any meaningful way and c) for us the second critical roll even adds to the thrill of combat. Of course, if none of these points is valid for you or your players, then better stick to one-roll attack resolution.
YMMV