Lately I’ve had a strong preference for group initiative. Despite individual initiative giving a more fluid and chaotic battlefield, as well as scope for per-character bonuses and penalties, it seems more trouble than it’s worth. Tracking who goes when is a hassle,particularly if you’re tracking each NPC separately, and players seem to get more bummed out when they consistently roll crappily than they are pleased to roll well.
But because I like to tinker, I’m considering the following house rule:
In order of preference each turn initiative goes to:
1. The side that ran away last turn, as long as they’re still running.
2. The side that downed the most foes last turn.
3. The side that hit the most foes last turn (failed saves count as being hit).
4. The side that rolls highest on a d6 plus any CHA bonus for the designated leader.
Tales of the Rambling Bumblers 
I am a fan of group initiative as well, especially when the character are suppose to be used to working as a team. It just makes more sense to me.