Just had a nice long LAN last weekend.
5 people, standard maps, once a large map.
A few rounds ancient beginning, one renaissance and one industrial beginning.
Sometimes no AI, sometimes 3 or 5 AI. CS between 10 and 16.
And it worked really well. No crashes or whatever.
But two things I noticed:
1. The turn-times go as fast as the weakest link. We definitely noticed the slowest computer holding everything up.
2. Civ5 and Windows XP aren't friends. One of us had XP, and he constantly had a hard time connecting. For instance, he had to be the last time to connect, otherwise he couldn't enter the game. The rest (three coimputers with 7, one with Vista) had no problems.
But overall I'm amazed how well Civ5 behaved. We put about 35 hours in, in three days, and on all computers the game was rocksolid and didn't crash once, nor were there any multiplayer-problems, like out-of-syncs.
What a difference compared to 6 months ago, when one could hardly even start up a multiplayer game.
So, basically, I don't have the same experience as the topicstarter and have experienced the opposites, MP being rocksolid since the last patch(es).