It's not only OSX/Linux, the Windows version is a bit embarrassing with its performance and graphics glitches too. I really hope they're using a different game engine for this one. Civ5 late games with massive maps are very tedious to play even with a beefy gaming desktop.

I think the AI turns are quite CPU bound with the current engine, so I agree. Late game end turns take forever to complete.

Last time I profiled it, most of the execution was in vsprintf. I'm pretty sure the answer is just “nobody put time for that in the budget”, as with multiplayer support.

Yeah, I have a modern macbook pro, but nothing I do on here sucks battery faster or makes the fan noisier than playing Civ 5.

FWIW, Steam reports 3.57% of users running OS X in April [1].

[1] http://store.steampowered.com/hwsurvey

Low user numbers are something of a self-fulfilling prophecy if it's a bad port in the first place, though.

That number is not for Civ V specifically, it is across a random sample of Steam users.