Hi there, Currently I'm running the latest version of Yosemite on a 27" iMac Late 2009. This computer has been upgraded though — now it has 12 GB of RAM and I replaced the SuperDrive with a 500 GB SSD. So first things first, I want to know if El Capitan is mature enough at this point, or should I stay on Yosemite. Be as honest and critic as possible — and please don't come with that story of how great the “new” OS is and how smooth it runs on your Mac. I've been a Mac user for some time to know that nothing works perfectly out of the box, specially during this Cook era, when you can expect things to have bugs and glitches months and even years after the release date. Also consider that I'm using an old iMac, and even if some of its components have been replaced, the performance could be even lower on the latest version of OS X (notice that this Mac has an i5 processor and a 4850 graphic card). Second, as I already mentioned, I took out the SuperDrive since it was broken. The thing is that after that I wanted to install Windows and it was a real PITA. You really are on your own out there, as there is no possible solution to install Windows on these old models without the SuperDrive. And I'll say again just in case: there is no possible solution to install Windows on these old models without the SuperDrive. Yes, there are some really dark methods out there that imply installing virtual machines, going to the Terminal and then even modify system files on the Windows side via DOS, but it's absolutely impractical and difficult. So, because of this, I had to use a borrowed SuperDrive and put it for a few hours on my Mac, so I could have Windows installed. After the whole process was completed, I replaced the SuperDrive by an SSD and then closed the iMac forever. I won't be opening it up again, so for me keeping Windows healthy in its Boot Camp partition it's almost a matter of life and death. Having said this, is there any chance (specially considering that I'm using an old version, i.e. Windows 7) that the OS X update might screw it up? I don't know, something on the Mac-BIOS level or something... Those are my questions. Truth is everything sort of works, so I feel tempted to obey that old saying “Don't fix what ain't broken”. Please guide me with your wisdom .