I will generally play against anyone. Having been a totally "green" player, not that long ago, I know one of the most frustating part of being a wet behind the ears "newbie" is not being able to get games with "veteran" or "crack" players (not to mention "elite"
)
When I first started playing PBEM, what allowed me to bring my game up to the next level was being soundly defeated by experienced players. When a player takes the plunge and goes from playing the AI to playing other players, he generally does it because he is looking for a new challenge.
I think it's the responsibility, nay duty, of every "crack" (or "elite"
players) to thoroughly trash a newbie every other week.