The action points worked well in practice and once you got your head around them, they were simple to use. They also brought a lot more realism and flexibility to the game. With AP I saw characters moving around a lot more seeking out tactical advantages through position.
The relationship between AP and rate of fire was pretty straightforward. You just multiply. Got a weapon with a RoF of 2? Spent two AP firing it at someone? That's four bullets. Got a weapon with a RoF of 1/2? (less common actually - tends to be just the big ones or sniper rifles). Then you need 4AP to get just two bullets off.
Everyone gets 4AP.
It let you put a lot more granularity into the game at no cost in extra tracking. You get shot at - want to Evade? Sure, that'll be 1AP, please. You spent them all firing everything you've got at people? Well, that'll learn you to keep some back next character. Better than juggling full and half-actions all the time, imo.
The fact that you could fine tune the AP was what led to my seeing much mire fluid combat as people would spend a little bit on movement and a little on firing or evading. You didn't have to keep track so much what someone had done - you just looked at if they had any AP left. I really liked it in practice. Combats usually went by more quickly in my tests. In a good way.