Hussar
Legend
I'm in the camp that believes it doesn't matter how much the players know because they are expect to roleplay their character, not themselves. I can read over the entire adventure before the DM runs it and have zero problem roleplaying my character and not my metagame knowledge. I failed my perception check against the gelatinous cube? Well okay then, since my character doesn't see it, he continues walking through the room and right into the center of the cube. Oh crap, I'm getting killed by a cube. Roleplaying. That's what I find enjoyable.
If another player wants to keep secrets from the rest of the group, then he can keep those secrets out of the game because he's playing a different game than the rest of us. If his character has secrets and he wants to keep those secrets from the rest of the party, then we roleplay that we don't know. The same way we roleplay that we don't know that the blue dragon breaths lightning, even though we've all read the monster manual.
If a player wants to hijack the game, they can sit out a session and I'll summarize what happened when I get a chance. I'm not running individual players off on their own. It creates imbalance in the group and is no fun. I play in an orchestra not a duet.
As I get older I find I much prefer a collaborative game than a competitive one and I find that players who focus only on their own objectives much less fun to play with and run games for. I also don't roll dice for players or hide my results anymore. It never successfully created the atmosphere I was looking for and I find it discouraged active roleplaying. I don't need to help the players roleplay by keeping information from them. I find it much more enjoyable when they actively work against their metagame knowledge. It also gives players an opportunity to enjoy and share in the experience rather than being surprised and emotional about it.
Those are just my preferences these days. I've done it the other ways for a couple of decades and now I'm doing something else. I trust my players to roleplay and they trust me not to ruin the game for them.
Cheers.
Can't posrep you, yadda yadda, but, this is, for me, very true.