A warning to Keith, you may not want to read this ! After two weeks of Yosemite on my 2008 iMac with 4Gb RAM I have no issues that I would complain about. The system feels rock solid, no bugs or lock ups with busy busy. I would definitely suggest that 4Gb RAM may be a minumum. This is because Yosemite uses RAM differently to earlier OS issues, though apparently Mavericks was similar. Because RAM has the fastest processing speed in the computer, the OS is taking advantage of this and fills the RAM ready for use, this is why a larfger capacity is more beneficial. With less RAM there is a longer delay when shifting between Applications as as more data is being swapped, particularly if several larger Apps are open at the same time. So my bottom line is that I get a short delay when moving between Apps but once there it is solid. Yosemite leaves memory in RAM if there is space so that when you open an App again it opens faster. Yosemite has also been designed to accept all third party applications that Mavericks accepted so you should not have any issues there. Other than that it seems most of this upgrade is to do with its look which doesn't apply to most of us, and it aligns the different Mac platforms together so you can work on your iphone, ipad or imac at the same time. This is through the Cloud. You are prompted to add this when Yosemite runs for the first time. You can also make phone calls through your desk or laptop so long as your iphone is within bluetooth reach. TF > > Click on the link below to go to our homepage. > http://www.icanworkthisthing.com > > Manage your subscription by using the web interface on the link below. > //www.freelists.org/list/macvoiceover > > Users can subscribe to this list by sending email to > macvoiceover-request@xxxxxxxxxxxxx > with 'subscribe' in the Subject field OR by logging into the Web > interface at //www.freelists.org/list/macvoiceover >