So, I've been thinking about the fast/slow ideas and can't get on board with it. I am certain people who use such systems have resolved my concerns, but here they are:
1. You roll every round. Not a huge deal, but I know a lot of groups don't like that. Also, since sometimes you will take only your action or move, and then other times you need to do both. This means one round you are on fast and the next slow.
2. The same problem with monsters. Some will need to move during their turn, others are already engaged so won't need to move. This means you basically need to roll two initiatives for monsters, a "slow" and a "fast" count, since most turns they will be mixed.
3. You can take the dice "out of the equation", but then it is basically up to the DM/players and theater of mind to decide who goes when. Sure, that can work but I can see it leading to issues.
4. For tables that do it by class, that is really off IMO. Having one class go before another all the time doesn't make much sense to me. For instance, I imagine many spells to be faster than bigger weapons. Still, if it works for you, that's all that matters.
I guess people who use such systems can comment and let me know your thoughts.