Currently, 4.1.12 is marked as stable though it's the last version in the 4.1 branch containing serious bugs in the intel GPU driver. Since 4.1.13 the issues are gone (== I haven't noticed any). #566102, #567164, #553250 are most likely caused by the bugs in the pre-4.1.13 versions.
I can confirm to be using 4.1.15 in production on like 20 servers (xen0, xenU, without virtualization) and no problems so far.
stable now.