I have PS3 and G27 as well, been looking for the same. I've only been messing with them for 4 hours and here's my settings so far:
All Deadzones at 1%
Steering saturation 30%
Steering linearity 25%
Throttle Saturation 10%
Brake Saturation 15%
- I don't like the fact steering linearity is so high, but without it it's way too twitchy on straights when I use "DRY" car set-up in "engineering".
FFB:
Environmental - 50%(default)
Feedback strength - 100%
Wheel weight - 75%
Notes: If I use cockpit view I notice significant steering ratio difference between my input and screen. Seems double or more, that is if I turn steering wheel 10 degrees, the on-screen "wheel" turns 20 degrees. Not a problem or complaint, observation only. GT5 and my settings for NFS UNleashed seemed very close to one-to-one.
Hope to see more G27 users post their settings and if/how they affect lap times and comfort. It's probably relevant to post whether you use any assists, I have turned all off.