Nothing special, I would say...
We started off with full complement 18 tribes, as 8 human and 10 ai.
However, almost immediately we had a dropout as Mr Cooper disappeared so we were +1 ai.
Game sped marginally when Ricketyclik was eliminated.
It really became fast after Kiwitt vassalled himself to Bismarck, to avoid the war he was having with both of us, so now we are down to 5 so fast is quite possible.
If we have more, the start will be slower, but that is quite normal, and generally more tribes = more fun.
The trick really is proven reliable players - although once in a while even one of those types will vanish without trace.
I personally am ready for another really large game - if we wish to combine Octafish and Angular participants on a huge map.
I would also be ready for an additional smaller game for those really keen.
For starters, I posted this:
http://forums.civfanatics.com/showthread.php?p=13867932#post13867932