My #1 computer is a mid-2010 27" iMac with a 2.93 Ghz Core i7 processor, 16 gb of RAM, and a 1 TB HDD. My iMac shipped with OS X 10.6. I have been going through the Apple OS X upgrade system since, and have used Lion, Mountain Lion, Mavericks, and now Yosemite. Last night, I re-installed Snow Leopard on a hard drive partition, and was reminded of how efficient that OS was upon using it for the first time in approximately 4 years. In terms of OS optimization, I am incredibly impressed with Snow Leopard. However, I know that subsequent releases have added useful new features, and I want to be entirely sure about my decision to downgrade before I take the plunge. So I'm asking all of you: should I "downgrade" from Yosemite to Snow Leopard? What would I lose? What would I gain? Is it worth it? Would El Capitan restore the performance gains I would have from downgrading to Snow Leopard? Thanks a lot.