Adobe said the problems will not be encountered by most people. The problems with cs3 are for certain workflow processes. I think cs3 will be fine on leopard. Adobe go as far to still recommend it for leopard.
While I haven't done much extensive work so far, I've used AE CS3 a bit on Leopard, and haven't had any problems. I fired up Premiere just to see if it would start, and it did, but I didn't do any work in it. But I haven't noticed any problems with either app yet (nor with Photoshop or Flash, which I've used a bit more since I upgraded -- though Adobe said that they'd be fine).
I've had 2 issues with AE CS3 in Leopard so far, one major, one minor.
The first one was when I tried to open a project I had started in Tiger, it had lots of 3d text layers using asian characters, and it would never preview a frame. I just got the spinning beach ball. Caps Lock made it go away. It's only happened on that one project so far, not sure if it has to do with the non-english characters (possibly a font issue).
The other one was scary, but not that bad. I was rendering out a sequence (created in Leopard) and suddenly the app disappeared! It didn't quit or crash though, just the interface window was gone (the menubar was there). The render completed successfully and I was able to quit and re-launch. it happened a couple more times while I was working, but I was able to save, re-launch and continue working. That one was random. The most recent time I was in AE, everything was fine.