4:39am and I finished reverting back to 10.9.5 Mavericks and could not be happier. After failing to wake it up from Sleep Mode for the 2nd time today (new 'bug' that started today)...that was it. Tried to deal with 4 days of extreme sluggish behavior, CS5 especially sucking the RAM out of this. I had to do it. Lot of work tomorrow and I had to do it now. My iMac actually feels faster compared to right before I upgrade to 10.10 on Friday. The whole process - restoring from Time Machine - was painless. For me it took roughly 65-70 minutes. After that, you simply need to login to your apps that use your Apple ID. Also check the App store for an important Security Update that was released over the weekend. Anyway, again I'm happy. I'll wait until Apple releases an update...and before upgrading again I'll wait on that update as well for potential problems. Right now, I am in no rush to update at all. For anyone who may want to do this, here are the steps. _______ The following tutorial explains an easy method to downgrade from OS X Yosemite to the Mavericks version. But make sure that you have backed up all your data before following the downgrade process. How to downgrade OS X Yosemite to Mavericks Downgrading to OS X Mavericks is an easy method. You need to install a Time Machine Backup of your Mac on OS X Mavericks, An External Drive is the best method **Also copy and save all your files from OS X Yosemite as you cannot restore a Yosemite Time Machine backup once you switch back to Mavericks. With the Time machine drive plugged in or available on the network perform the following: Click on the in the upper left and choose Restart When Mac is restarting press the Command and R keys together until the screen turns grey **it took me roughly 3-4 minutes for the screen to turn gray, be patient, do not panic. ** On the next screen choose Restore from a Time Machine Backup and click Continue. Click on Time Machine disk then choose the backup you want to restore. Ensure this one is with Mavericks. **If choosing the main Macintosh HD, It will state "This will Erase your Mac HD, are you sure you wish to continue?" Prompt looks scary, but everything from your Time Machine backed up (Programs, documents, photos) will show up when restore is compete** Once you have finished the backup, follow the on-screen prompts (Apple ID logins) to complete the installation and restore from backup. _______________ Note: Without backup you can still downgrade but you need a USB drive and you can manually back up all your data. But this is likely to take a little longer. You need to create a clean install of OS X Mavericks and then move your files back to the computer. But be careful while doing so as updates like these can change file structures and libraries used in apps. Download OS X Mavericks from Mac App Store Open the Mac App Store, click on Purchase then find OS X Mavericks, click Download then click Continue and wait for the download to complete Click Install on the pop up that appears. Ensure that you have backed up all data as the following step will delete your data Step-1: Connect the USB drive and open Disk Utility Step-2: Select USB drive in the sidebar and click on the Erase tab Step-3: Select Mac OS Extended (Journaled) in the Format box and name it as Untitled Step-4: Click Erase and wait for the format to get completed Step-5: When the format is completed, close Disk Utility and open Terminal. Enter the following command and press Enter sudo /Applications/Install OS X Mavericks.app/Contents/Resources/createinstallmedia –volume /Volumes/Untitled –applicationpath /Applications/Install OS X Mavericks.app –nointeraction Now you should wipe your hard drive and install OS X Mavericks. You should see OS X Mavericks running on your system instead of Yosemite.