I think you're right Dennis. I'm running Yosemite on a 2008 MacBook Pro and it works pretty well. I only notice a bit of dragging if I get more that than about 3 or 4 apps open at once. I do have 8 GB of ram installed though.
A lot of how well it runs will depend upon the tasks you run regularly and how intensive they are.
Shop for your Apple, Mac, iPhone and other computer products on Amazon.
We are a participant in the Amazon Services LLC Associates Program, an affiliate program designed to provide a means for us to earn fees by linking to Amazon and affiliated sites.