Now that answer is not entire correct i guess, since in the boinc community we used much older versions like 10.11, 10.12 and when you install those opencl do not work, you have to install sdk 2.1 to get stream and opencl working.
So i guess that has been passed on to all following versions even though i think from 11.2 the opencl driver should be working with the standard install.
These old version do not have the cpu bug at all, but i found cgminer not able to run with this driver.
Installing sdk 2.5 did not solve the problem, so i had to install one of the bugged ones to get the card running with cgminer again.
I have not tried any of the other miners because for me the cgminer is the best ever made.
Especially since phoenix allways seem to have aproblem connecting to the pools on my machines and all others are much slower on my cards.
And most important cgminer has so darn many nice options which can be set
, i simply love it.
Till today non of the opencl group have tried to solve this opencl problem as far as i know.
And yes JackRabitt the fastest is still 2.1 in the boinc community but ofcourse program makers do incorporate new things from the newer sdk's so you end up with not good working programs. But i can promise you that sometimes you see fake results as well.
I had installed 11.10rev3 and i suddenly had 104 Mh/s on a 4770 which in fact does around 65 Mh/s so it simply was showing bugged numbers
To answer on other people mention sdk 2.2, 2.3 and 2.4 as being good, well lol i have bad experience with them on windows and no i do not have a clue about linux i hardly use it anymore