My hash rate is about 10% lower with the newest cgminer. I should be able to use the same config file right?

You answered it good enough. I can just use the older version. I would probably lose more then I would gain messing with my rig drivers.

I renamed the original cgminer as a backup, and did a fresh install of the new version with a copy of the config file. I then realized the hashrate was wrong, deleted the new copy and renamed the original and its working fine again. What could have been messed up?

For anyone who has set this up is it just:

"api-allow" :  "W:172.0.0.1, W:192.168.0.100",

assuming you want host 192.168.0.100 and local access to modify the settings through the API.

I think kano is right. At least it was the reason preventing me from updating from version 2.1.2 since phatk opencl code has changed and cgminer had to recompile (or whatever it does with .bin files) it.

I had trouble deleting APP SDK runtimes. Somehow it stayed in the system after uninstall.
Here's what you need to do:
1) Uninstall either APP SDK runtimes or whole Catalyst suite through AMD uninstall utility.
2) Search for amdocl.dll and OpenCL.dll in Windows directory and delete them
3) In case you uninstalled whole suite, reinstall it with custom install and uncheck APP SDK runtimes
4) Download and install needed OpenCL driver. Older version avalable for direct download here:
http://support.amd.com/us/gpudownload/windows/previous/Pages/radeonaiw_vista64.aspx
http://support.amd.com/us/gpudownload/windows/previous/Pages/radeonaiw_vista32.aspx
http://support.amd.com/us/gpudownload/windows/previous/Pages/radeonaiw_xp.aspx
For newer versions - download suite, install and select only AMD APP runtimes. You can backup OpenCL.msi from AMD/ATI temp directory on C: for future use.

You can choose driver version according to needed SDK version:
http://developer.amd.com/sdks/AMDAPPSDK/downloads/pages/AMDAPPSDKDownloadArchive.aspx

I've started to get ztex boards supported on cgminer. The current implementation uses libusb-1.0, compiles cleanly on linux (ubuntu, but all others should be fine) and osx (snow leopard here). I'll try to make it work for windows soon; https://github.com/nelisky/cgminer/tree/ztex

This is not feature complete, not all that tested so be careful. I have been mining with it for a while and the biggest caveat is that the hash rate measurement is completely broken. It seems cgminer doesn't like when I do a full nonce scan that can take 12~15 secs and only report the calc'd nonces at the end of that. Limiting the nonce space does make it report correctly and of course the actual speed is the ~200MHs expected from the board regardless of what cgminer reports

But what I'd really like to put in, and I'm not sure if this will be well supported in cgminer, is hotplug support. Will I be able to dynamically add remove workers? Should I use a main worker thread and then spawn child threads, one per board? I would also like to use multiple boards per thread and just split the nonce space, as there is enough time between polls to handle that.

Opinions? Pointers? All well appreciated

The default is ~/.cgminer/cgminer.conf
(You must use ls -a to see file/directory names which begin with a ".".)

So to remove:
rm -ri ~/.cgminer

Funnily enough my 2.3.1-2 doubled up on the poo front. Not using the conf file, and only happened this one time. Haven't re-started it to see if it does it again at all. It's not affecting anything so I've left it.

3 possible Causes:
1) in the "-c conf" file specified and also specified on the command line
2) in the "-c conf" file specified and also in the default conf file
3) specified on the command line and also in the default conf file

Yes, the default config (cgminer.conf) if it's able to find one.