Hi @ll
My first post here... will try to help as much as I can (and ask as little as I must)
First of all, thanks Buchner for making this possible!
I have two "average" working rigs mining at the moment, so I'm going to share my xp hoping to help all users and developer.

Gainward GTX 570 1280MB phantom @ stock (running on intel E8400, 4GB/1066, Asus formula rampage, all @ stock)
Gigabyte GTX 760 2GB OC @ stock (irrelevant in this case, but i7, 16GB, Z87... too good to make any "noise" anyway)

Anyway... after 4-5 days in testing, I have got the best results with Cudaminer 2013-12-01, 64bit in both cases (2013-12-10 not tested on GTX 570).
Both rigs running on Win7 Pro X64 SP1 with various (different for sure) official updates...

GTX 570 config (max 255KH/s):
cudaminer.exe -i 0 -H 1 -l F15x16 -C 1 -o stratum+tcp://...
All other auto or manual configs work with lower rates, but never below 200KH/s (I'm talking about "correct settings" for this card, not random Fxxxx)

GTX 760 config (max 177KH/s):
cudaminer.exe -i 0 -H 1 -l K96x2 -C 1 -o stratum+tcp://...
this is MANUAL config, because auto NEVER gives me this setup! All other configs are lower, but not lower than 150KH/s.

My next post will be about some odd things on both rigs, which hopefully can be eliminated or "refined" in further development...

Anyone with better configs/setups are welcome... we all love to try something better!

P.S. All of this is obviously very different on every system, so EVERY SINGLE component in our rigs can make a serious change in hashrates.