I can only speak for my own personal experience, and I'm a big fan of icehancer 1.25:
Still the second most downloaded graphics mod, if you'd like to see some screens I've got plenty:
The only bug is the red-sky bug you'll find with most graphics mod, it's when you look in certain angles the sky turns red. I'm not really bothered by it since the beauty of the mod makes up for that bug
As for AI, there are some scripts around like Arrest warrant:
I use it myself, it makes the cop react to you more. If you drive above the speedlimit, drive the wrong way, hit other cars etc they will pull you over.
You also stay wanted a while after you've lost the police (if they've identified you or your car)