Wow I should've stumbled upon this thread half an hour ago. I'm downloading Yosemite right now as we speak and I have a 2010, 2.4Ghz MBP 15" w/ 4gigs of ram and 320GB HDD + 120GB SSD fusion drive. Mavericks runs perfect. We'll see how it goes with Yosemite but iCloud Drive is a must for me because of work. (I have to access up to date files both from my Mac and iPhone and no I don't like using non native things like Dropbox, Google Drive although maybe I should)
I also gotta add I don't plan on buying another computer for myself till 2016. Hope my good old Mac can make it. I might even delve into changing the wifi card and modifying kext in order to use Handoff + Continuity. (only interested in using my iPhone from Mac to send/receive SMS & Calls, don't know whichever one is continuity and vice versa)
p.s. SSD fusion drive thing from the terminal via a tutorial I found online has elongated my Mac's life drastically. Did it back towards the end of '12 and as it stands, as a 4.5 year old laptop speed is great, battery is around 3.5 hours, which I think is also great.