My ideal group would be one where everyone got along well, and understood each others expectations. For instance, while I am into everyone staying in character and not disrupting the game often with non game chat, I also would be uncomfortable in a group where everything was 100% in character and no one felt comfortable enough with each other to joke around at appropriate times.
I like a group where every tries to play their character and combines roll playing with role playing. I like when people get into their characters, but not so much where they become judgemental and snippy if someone breaks character to ask a question once in a while about a rule. People should know the basic rules, but I learned as I went along and have no problem with others doing so, although , when someone doesn't know what dice to roll for their damage every game for 12 weeks, that might get old real fast.
I guess, for me the ideal group lies somewhere in the middle of the "die hard in character no out of game talk group" and the "nothing is serious let's stop the game every 10 minutes, rules; what rules? group".