Upgraded to snapshot r17216-8c2509dc5f via attended sysupgrade on my second E8450. Random MAC issue is gone, but last night it appears to have locked up. I have remote syslog set up and everything looks normal until this at the end:
Jul 29 22:13:48 ap-lsys-cc kernel: [76507.624097] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000053
Jul 29 22:13:48 ap-lsys-cc kernel: [76507.632912] Mem abort info:
Jul 29 22:13:48 ap-lsys-cc kernel: [76507.635697] ESR = 0x96000005
Jul 29 22:13:48 ap-lsys-cc kernel: [76507.638756] EC = 0x25: DABT (current EL), IL = 32 bits
Jul 29 22:13:48 ap-lsys-cc kernel: [76507.644069] SET = 0, FnV = 0
Jul 29 22:13:48 ap-lsys-cc kernel: [76507.647116] EA = 0, S1PTW = 0
Jul 29 22:13:48 ap-lsys-cc kernel: [76507.650272] Data abort info:
Jul 29 22:13:48 ap-lsys-cc kernel: [76507.653149] ISV = 0, ISS = 0x00000005
Jul 29 22:13:48 ap-lsys-cc kernel: [76507.656977] CM = 0, WnR = 0
Jul 29 22:13:48 ap-lsys-cc kernel: [76507.659957] user pgtable: 4k pages, 39-bit VAs, pgdp=00000000418a9000
Jul 29 22:13:48 ap-lsys-cc kernel: [76507.666441] [0000000000000053] pgd=0000000000000000, p4d=0000000000000000, pud=0000000000000000
Jul 29 22:13:48 ap-lsys-cc kernel: [76507.675158] Internal error: Oops: 96000005 [#1] SMP