Today I loaded a Byzantine start on my pc (about 420 turns IIRC) in 11 minutes. I think about 25 to 30% of the map is actually habitable since the empty zones in Russia, Tibet and Indonesia are quite big, although the latter two may be settled in the late game, I have never played beyond 330AD and it has been a while since I loaded a 320BC Frankish start. In the Egypt game I'm playing now there are about 85 to 90 cities in 113BC, but the habitable area is almost full. Funan and Japan are still empty, the Khazars and Tibet haven't spawned yet, but I don't think a normal game exceeds 100 or maybe 110 cities as late as 600AD.
What also speeds up the game I think is the number of units. This is because of two reasons: the first is the impossibility to build mines on hills. I can remember me actually opposing (did I?) this change, at least I wasn't much in favour of it. However, I like it now. Egypt is developed very quickly but slaves have a second use, to rush buildings and stuff so you won't just delete them. The second reason is the relatively small size of each civ. Units are always near their borders, so when the AI needs to use them, they can. They are never sitting in an in-land city that is so far away from action that the devensive stack is never used.
