all the problems were at release. it is much, much better now. HOnestly, I haven't played it much since the major update, but it's still quite good.
the guy who did Fall of Heaven (the big, popular, fantasy-based mod for Civ 4) took over as lead designer, and his campaign mode is supposed to be released in a few months, I think.
I assume it doesn't matter what you pay now--but I do know that anyone who purchases it before that, will get that for free, as well as the first major expansion which is due in the winter *I think*
It's a shame, the game was rushed out way early and horribly buggy and clunky. Actually, it seems a lot harder now. I've tried to start a few games with the new overhaul and I keep getting owned early on, haha. I have to figure out the new mechanics.