Ok, let's start with this : - I know it's a Developer Preview - I know it's full of bugs and I'm not complaining - I know that not all apps are going to work Why do I want to do this : I own a 15" Late 2013 Macbook Pro with Retina Display with a 256GB SSD and I'm running out of space with 2 partitions. a) Mavericks - 200GB / Free 18GB (I store all my movies on my 3TB NAS Server) b) Yosemite - 50GB / Free 21GB If I install Yosemite as my Main OS I can get a lot of free space back. - I paid the 99 bucks to get access to this betas so I want to play with them with no restrictions (an example of a restriction is running out of space). - Yosemite has recieved 3 updates so far ; that's a lot of bug fixes and new features. - I have a bug with Mavericks which is driving me insane. I've been playing with DP3 for a couple of days and I must say, it's far better than the previous DPs. Why I don't want to do this : - Even if it's been updated 3 time since June, it's still a beta which means : a) The system could crash at anytime (i haven't experienced this yet but you never know) b) You can never trust the readings (for example, battery) on a beta OS c) The apps I use the most work with Yosemite but maybe I'll buy an app tomorrow which does not work with 10.10 As you can see, I have the same number of pros and cons on this. What should I do ? I wan't to know your thoughts.