I got my nMP in May and had a lot of problems: 1. One monitor did not wake up reliably when nMP woke up from the sleep mode. 2. nMP froze while booting up. 3. When using VGA monitor, the monitor blinked. 4. It had some problems entering sleep mode initially. After 5 months of debugging, I finally got it under control. AppleCare provided no help at all. Even though they got their Engineering dept involved in debugging my issues, they provided no solution. So finally I have a stable system. This is a home computer and I occasionally do some scientific/engineering programming. So I am wondering if there are any good reasons for me to upgrade to Yosemite.