I dm for groups and play in a few. Combat can be quick and sweet if everyone at the table knows the bloody rules and its muddy and slow in groups that dont. .
After nearly three years of alternate weekend games, our current group (stood down at present) has picked the rules up well enough that combats go quickly and smoothly. We do, however, have a girl who still forgets what die to roll and how much damage she is meant to be inflicting with a longbow. The round inevitably stalls when it reaches her, and she rarely has anything planned for her turn. It is frustrating. Luckily we are a fairly mature and well-balanced group so nobody has yet stood up and told her that she is an anchor around the group's neck. She's a lovely person, but my gods it is frustrating to play RPGs with her.