Just got my 8 year old iMac back off my In-Laws as they've just upgraded to a MacBook Air as they are moving from a house into a flat so no room for a 20" iMac. First thing I did upon getting it home was to install a fresh install of OSX 10.11 El Capitan DP1 to see how it runs compared to me mid 2012 Non Retina MacBook Pro. I did a clean install off a USB stick and then used migration assistant to move all my stuff from my MacBook Pro onto the iMac so its basically a clone of my MacBook. All I can say is WOW! For an 8 year old machine it runs surprisingly well, very little lagging, animations are smooth, and generally it runs very well. I am rocking a base model 20" iMac Mid 2007 with upgraded Ram to 3GB, 320GB HDD, 2.4GHZ Core 2 Duo, ATI Radeon HD 2600 Pro with 256MB of memory. So this is basically the lowest spec machine (bar the extra gig over minimum of RAM) that will run El Capitan. A few things I have noticed are occasionally when interacting with menu bar over videos playing in Safari the videos drop a few frames and appear to stutter (Netflix) Also surprisingly as this machine doesn't support AirPlay mirroring due to its age, the AirPlay icon appears in Safari as if it could send the video to the AppleTV although not tested yet as wife is using the TV lol. Overall though very very pleased with the performance given the age of the machine and being above minimum but below the recommended RAM. Anything anyone wants me to try and test (as long as it doesn't require paid for apps) let me know.