David,
I have an 82 911. Here are a few things I can think of off the top of my head:
Even if the AC is working properly, it sucks.
Expect oil leaks no matter what and a little puff of smoke at start up is nothing to worry about.
The car is small. I'm not that big of a guy (6'1" 210lbs) and I am very uncomfortable in the car when I have a helmet on. Also, if I have a friend in the car that is about my size, our shoulders just about touch.
The car is fun but since I got the Box in Dec., I haven't really wanted to drive the 911. That's not a knock on the SC, I just think the Boxster is that good.
The only thing the SC has over the Box is that it is much more photogenic:
