I have been running two test boards of the 1.15y (and three 1.15x) for a few days now (licensed production).
001-0: ztex_ufm1_15y1-0000004-01-1: f=228.00MHz, errorRate=0.00%, maxErrorRate=1.07%, hashRate=228.0MH/s, submitted 17 new nonces, luckFactor=0.96
001-0: ztex_ufm1_15y1-0000004-01-2: f=232.00MHz, errorRate=0.00%, maxErrorRate=0.50%, hashRate=232.0MH/s, submitted 13 new nonces, luckFactor=1.02
001-0: ztex_ufm1_15y1-0000004-01-3: f=232.00MHz, errorRate=0.54%, maxErrorRate=0.99%, hashRate=230.7MH/s, submitted 12 new nonces, luckFactor=0.96
001-0: ztex_ufm1_15y1-0000004-01-4: f=224.00MHz, errorRate=0.25%, maxErrorRate=0.97%, hashRate=223.4MH/s, submitted 18 new nonces, luckFactor=0.98
001-0: ztex_ufm1_15y1-0000004-02-1: f=224.00MHz, errorRate=0.00%, maxErrorRate=0.65%, hashRate=224.0MH/s, submitted 12 new nonces, luckFactor=1.00
001-0: ztex_ufm1_15y1-0000004-02-2: f=228.00MHz, errorRate=0.33%, maxErrorRate=1.38%, hashRate=227.2MH/s, submitted 10 new nonces, luckFactor=1.05
001-0: ztex_ufm1_15y1-0000004-02-3: f=232.00MHz, errorRate=0.69%, maxErrorRate=2.62%, hashRate=230.4MH/s, submitted 14 new nonces, luckFactor=1.00
001-0: ztex_ufm1_15y1-0000004-02-4: f=220.00MHz, errorRate=0.00%, maxErrorRate=0.00%, hashRate=220.0MH/s, submitted 7 new nonces, luckFactor=1.00
001-0: ztex_ufm1_15d4-04A3469722-1: f=216.00MHz, errorRate=0.00%, maxErrorRate=0.66%, hashRate=216.0MH/s, submitted 13 new nonces, luckFactor=0.97
001-0: ztex_ufm1_15d4-04A346CEC7-1: f=216.00MHz, errorRate=0.08%, maxErrorRate=1.19%, hashRate=215.8MH/s, submitted 11 new nonces, luckFactor=0.94
001-1: ztex_ufm1_15d4-04A32E00E9-1: f=212.00MHz, errorRate=0.00%, maxErrorRate=1.35%, hashRate=212.0MH/s, submitted 15 new nonces, luckFactor=1.00
001-0: poll loop time: 123ms (USB: 11ms network: 112ms) getwork time: 262ms submit time: 260ms
001-1: poll loop time: 14ms (USB: 0ms network: 14ms) getwork time: 391ms submit time: 337ms
Total hash rate: 2459.6 MH/s
Total submitted hash rate: 2421.3 MH/s
Total Device #01: 913 MH/s
Total Device #02: 901 MH/s
The last 3 units are 1.15x.
Room temperature is 25C, I am using the stock heatsinks with fans. They are very stable and I have seen even more impressive hash rates (had them running on <20C AC for a while).
Connected to a low cost Atom board with 2GB memory running Ubuntu, using 0% CPU load average 0.00.
Currently all (incl. Atom) powered by a very inefficient 350W Mini ATX PSU. My kill-a-watt device shows 199 Watt at the wall. The Atom board alone is 27 Watt.
It will be interesting to see what happens if I move to a better PSU and passive cooling without the 11 small fans.
In the photo above I was experimenting with different heatsinks. While the ones on the right are easier to mount (the mounts are attached to the heatsink) they were too noisy and so I replaced them with the stock heatsinks after two days (can't take a new photo, logged in remotely via RD then on to VNC to the Ubuntu box).