I have many of the issues reported here, specifically massive slowdowns (although I experience them around 0AD). It really seems that the slowdowns occur when the AI gets too busy - if I keep my exploration to a minimum I notice my speed stays relatively consistent (until the inevitable CTD). Also, bringing up the right-click menu consistently destroys mouseovers fromt hat point on. However, the CTD is almost always associated in some way with my graphics drivers, leading me to believe that much of the slowdown is merely bad DIrectX implementation.
I have the latest patch (v1.09). I will wait patiently until a patch is released, but I gotta say - I can't blame the developers for this. This reeks of a lack of quality control and there are only one brand of people that make those sorts of decisions - executives. And the comments made about "they've got our money, now why bother"... well those may be a bit unfair, but returning the game to the store you bought it from can really light a fire under the bean counters.
Sid, shame on you for letting this one hit the stands. This is worse than CTP. I love your games, I'm a firaxis addict, but this is really poor form. I expect this sort of buggy behaviour from FPS games and such, but frankly the FPS crowd has been getting better while you guys have obviously gotten worse.