Tried out Rjb82's settings with 13.1 drivers on ubuntu linux 12.10, doing 1100eng/1500mem/20intensity, working well at 648 Kh/s on SAPPHIRE Vapor-X 100352VXSR cards.
Not to hot except for one which has riser cables in the way in my rat's nest ghetto milk crate build.
Thanks Rjb!

If anyone's on linux, here's some settings that worked well for me:
(warning, unix nerdery below)

1. create a bash script , i.e. run_cgminer.sh

#!/usr/bin/env bash
export DISPLAY=:0
export GPU_MAX_ALLOC_PERCENT=100
export GPU_USE_SYNC_OBJECTS=1
export GPU_MAX_HEAP_SIZE=100
cgminer --scrypt -c $1 ${@:2}

2. I then put the config details into a JSON-formatted .conf file, such as:

{
"gpu-engine" : "1100",
"gpu-memclock" : "1500",
"intensity" : "20",
"thread_concurrency" : "16384",
"vectors" : "1",
"worksize" : "256",
"lookup-gap" : "2",
"temp-target" : "70",
"auto-fan" : true,
"scrypt" : true,
"pools" : [
   { "url" : "stratum+tcp://luserpool.com:3333",
     "user" : "LTC4CO2",
     "pass" : "LTC4CO2"
   }
]
}

3. then I call run_cgminer.sh (don't forget to make it executable with %chmod +x run_cgminer.sh) with the .conf file as an argument, and any arguments I want to add:

%run_cgminer.sh somefile.conf [ extra arguments ]

4. actually it's nice to use a program like 'screen' to keep your terminal session alive even if you log out / get disconnected. Screen is like a terminal server
a - ssh in
b: %screen -R -D cgminer_session
c: start cgminer script
d: detach from cgminer session with ctrl-A, d
later on ssh in again, re-attach to cgminer session with %screen -R -D cgminer_session

5. getting cgminer to start automatically on boot is left as an exercise for the reader. Note, you must have an X session running.

6. bonus points for automatically rebooting when GPUs lock up.