Has the option to manually set diff been implemented yet?
Good news: you may now set a manually difficulty setting by using d= as your password.
For example:
cgminer --scrypt -o stratum+tcp://mine.coinshift.com:3333 -u 1L38dYqRtfZUMcKRN3Jfb1b1hvCqKiXE3Q.miner1 -p d=512