With the core PHB, it was ok. I could pretty much grok what all the classes did, what the major class features where, etc. I knew that Clerics & Paladins had Channel Divinity, Defenders had marks, etc.
I'm playing in an online 4E arena game where out of about 16 players, teams of 4-6 are put together on an adhoc basis for a series of 3 encounters. Everyone is in the low or mid levels. At this point I just can't keep track of what abilities everyone else has. Luckily, WOTC has actually done a decent job of enforcing role boundaries so I know what I expect a defender, striker, leader, or controller to do. But they have not done a good job of enforcing power source boundaries. Plus, the plethora of new powers makes it hard to keep track of the options for just one class, much less the rest of the playing world.
I think a better approach would be to have a series of "menus" with limited (5-9) options. For example:
- Pick a role (Defender, Leader, Striker, Controller, perhaps multiclass)
- Pick a power source (martial, divine, arcane, primal, psionic)
- Pick a style (offensive, defensive, balanced)