Be careful with this update. I didn't read well and after reading few posts on Macrumors forum regarding this I went ahead and upgraded OWC SSD 120GB in my Mac Pro 5,1. Problem is that some users on this forum are writing misleading informations regarding "sleep" issued being fixed. In fact you can't force your Mac to hibernate without installing any extra software.
The firmware update fix hibernation issue and not sleep issue. I was surprised because I have never heard before about hibernation on Macs, so I simply thought it's regarding sleep issue.
For the sleep issue to get fixed, you have to physically send SSD to OWC to have this fixed. Sleep (wake up -> freeze) issue is easy to reproduce:
1. Set computer sleep in energy saving preferences to 1min
2. Wait until it fall asleep
3. Wake it after few minutes
4. You can't do / click anything as the system is frozen.
The sleep issue is only caused when system force the disk to sleep automatically. If you set "computer sleep" setting to never and will always "sleep" your mac manually, it works properly.
The only thing I have noticed after firmware update is that now my Mac Pro won't go sleep automatically. But what's worse I have noticed 10% speed drop while testing on 4GB while few times (using AJA System Test) before and after the firmware upgrade.