I have been gaming for nearly 30 years. I have played Dungeons and Dragons since 1st edition, and jumped ship after seeing 4E. I now play Pathfinder. Only Pathfinder. As a GM, I might not know all the rules, and I might mix things up with 3.5. But ultimately, I still try and keep things fun. As a GM, I might take a couple minutes to look something up, but I prefer to make a decision and if needed, talk about it on the forums. I despise metagaming. Keep player knowledge separate from character knowledge. Yes, you know trolls regen, I know trolls regen, we all do! However, Cromax the orc barbarian with an Intelligence of six and no ranks in knowledge local does not know trolls regen, and your wizard doesn't have the skill to tell him. When the ranger or rogue remember they can roll on it, they can tell you! Till then, you have no clue about it.