This old 3.5e blog post caught my eye on Twitter. The gist of it is that individual player initiative ruins the game, and I have to agree: Players zoning out when it's not their turn has been a problem ever since the concept was introduced. Even round-the-table ordering didn't really prevent it. Almost every table has at least one person who spends their time between turns flipping through the rulebooks, doodling on their character sheet, or running to get a soda from the fridge. In some games, that's nearly everyone at the table. That leads not just to detatchment from the game, but slows it down for everyone else since they have to catch back up every round. In a particularly tactical game like 4e, that can be deadly to the party.
Here's my idea for helping counteract that, and at the same time help speed up combat: A pre-round huddle. Everyone rolls individual initiative as normal. Everyone who beat the monsters initiative takes a moment to plan out their actions for the round, then they act in initiative order. If you roll initiative for individual monsters or groups, you may wind up with the party split into multiple initiative groups. As suggested in the other article, I would exclude whoever rolled lower than the monsters from the initial huddle, then do the pre-round huddle on the straggler's turn to bring things back around. If there are PCs stuck between monster initiatives, you could either give them their own huddle or leave them out of the huddle. That last would be particularly appropriate if they're also physically separated from the party.
The idea here is that you involve everyone in the whole combat by giving the party an explicit period for planning out their whole round, and when the time comes to perform the individual turns everyone already knows that they're doing. Keeping the individual actions ensures that various feats that grant initiative bonuses keep their value. Individual actions should go quickly, since they should just be the DM confirming that they still want to go with their planned action and then calling for the roll. You can rationalize the coordination (if you're into that sort of thing) by saying you're consolidating the regular inter-party chatter that happens throughout the combat. That also makes it a good place to interject NPC threats and taunting. Most importantly, it encourages the party to work together on the combat round instead of considering just how much damage they can do to the bad guys on their turn.