Hi everyone, I have the BTO i7 2009 iMac (the first 27"). I have since ripped out the dvd drive and replaced it with an SSD that has the OS and programs on it, and kept the 2TB internal for music/movies/photos. I also have 8GB RAM. On Mavericks it used to run pretty much buttery smooth, with very little lag. But since upgrading to Yosemite beta, and then even after doing a clean install of the RTM, I have gotten quite significant lag. Just doing usual things around the OS like switching programs, changing views in iTunes, switching between tabs in Safari, using Mission Control/Expose/Launchbar. Watching Netflix in Chrome at full screen also is often half of second out of sync between audio/video. It's not bad, its usable (and better than when I just had a platter HD) but its usually a second or so of lag when doing any of those things. Perhaps I'm remembering wrong, but I didn't have the same problem with Mavericks. So can you please post how your 2009 iMac is doing with Yosemite? Specifically, I'm wandering if it is the RAM that's the problem (I am consistently getting around 200MB of swap, and significant paging, but the memory pressure is always green, and 8GB of RAM should be plenty to run OS X. It's not the hard drive, because I have an SSD. Is it the graphics card (which was quite underpowered already at release)? I don't know. So I don't mind getting more RAM if necessary, but don't want to pay $150 for another 8GB of RAM if the problem is something else. I suspect graphics, if only because older games I can remember playing on medium or high graphics settings at purchase now only work on low, and then sometimes at <20 FPS. How is yours doing? Please state model, RAM amount, HDD or SSD, etc. Thanks!