I've played face to face and by email. They are really different games but playing by email is really quite fun. The tempo is different and the games take on an epic quality. A typical play by email game will lasts 3-6 months and can go longer. You'll often be waiting days to find out the results of some critical moves. Over email there is an entirely new class of interpersonal tactics ("Oh I must have missed your email asking for support - I'm so sorry!", forwarding messages from other players, etc.)