I started playing Civ5 using a Wineskin port before there was ever a Mac version... then switched over to playing the Mac version when it came out.... and still play it from time to time. I never had the game crash at all, so no idea if the crashing problem is fixed since I never had a crashing problem...
Civ4 has some good things about it... but overall I find Civ5 to be a much better strategy game. Later games in Civ4 get really boring since you can just make like 100 units and stick them all in each of 50 squares and roll through devastating everything... Civ5 with unit stacking rules adds MUCH to the strategy and uses of specific units. For that and the hex grids alone I play Civ5 any time over Civ4. After a few expansions over the next few years on Civ5, I'm sure it'll be better than Civ4 in every way.