I'm testing latest GIT build of v5, and I have a few drop in hashrate compared to dedicated miners :
This is for a R9 280X Tri-X
Scrypt : v5 = 755 Kh/s, ref = 760 Kh/s, it's OK
X11 : v5 = 3,2 Mh/s, ref = 3,5 Mh/s, it's less than using sph-sgminer_x11mod (https://github.com/lasybear/sph-sgminer_x11mod)
X13 : v5 = can't compile .cl files at start, should be a bug introduced recently, ref = 2,45 Mh/s (same as X11)
Keccak : v5 = 380 Mh/s, ref = 370 Mh/s, OK
Nist5 : v5 = 7 Mh/s, ref = 13 Mh/s, it's VERY BAD DROP !

Maybe I'm missing some important tweaking (each miner have his own configuration when using different kernels) but using V5 drop hashrate on most cases.
If you have suggestions (config files), post them.

Thanks.