I'm using Claymore's ZCash AMD GPU Miner:
https://bitcointalksearch.org/topic/claymores-zcashbtg-amd-gpu-miner-v126-windowslinux-1670733
I have a Radeon 280x and getting 290 S/s
Here's the command I use:
ZecMiner64.exe -allpools 1 -zpool mine.zpool.ca:2142 -zwal 1MkmBHDjonAFXui6JEx9ZmEemfMtUo9Cmu -zpsw equihash
However, it does not exit/close when the profitability changes like cpuminer. So far cpuminer is the only one that behaves properly with your pool when profitability changes (exits out so the next line in the batch file is executed).