You sound like me - desperately hanging out for TOCA Race Driver (or V8 Supercars as it will be here).
GT3 is somewhat passionless - the actual experience of driving the car is superb, but as you say the AI is a bit of a disaster, and does let the game down - hopefully TOCA will force them to raise their game in this area.
I actually dragged TOCA World Touring Cars out last night. I almost vomited when I saw how bad the graphics are, but within ten minutes I was racing door to door with the AI, trying to pass under brakes, defending my line - fantastic!