I have an ATI card but never ran into any technical bugs.
The script bug however I did come across, and it annoyed the hell out of me. So I went and checked forums for a resolution to the problem, but like you said the only way was to load an earlier save, which I had none. So I restarted the campaign aware of what NOT to do, and played it through 'til the end without any further problems. The second playthrough it took me less than half the time to reach the same point since I had more experience, but still. I can see why that would make you give the game up.
I still loved it though, simply because there's nothing like it. Give me a Fantasy:Total war with heroes and magic and I'll forgive the gaming industry for everything. Except Dragon age. And Fallout 3. And maybe some other game I've forgotten to mention.
But as far as I'm aware the Total War people only want to make (kind of) historically accurate games. To bad. So I'll buy this game instead, without a moments hesitation.