I have a MacBook Pro Mid 2012 (MacBook Pro 9,2). Few years ago I was using previous versions of Mac OS X, and it was a great experience. I've found it delicious OS for personal use.
Today I use Yosemite and performance really slows down. Safari takes about 15 seconds to open, and 5 seconds to be ready for use. Terminal takes about 7 seconds to open.
I don't see the reason to buy new hardware, because i don't see any advantages in Yosemite. It has more simple design, but it works much more slowly. Okay, in theory I can receive cell calls on my MacBook Pro. But it takes about 10 seconds to show incoming call and to make it possible to click "answer".
I've removed all applications from automatic boot. I've cleared my HDD. I've tried almost everything and there were no results! It still works very slow!
Today I've tried Yosemite on the same hardware (Core i5, etc.) and it works really fast. Two differences are: it was Mac Mini and it was late 2014 model. I don't believe that Safari or something else requires new hardware to work normally. It seems like Apple just force me to buy new hardware. I guess in a year my MacBook will work like a turtle!?
So what can I do to improve my MacBook performance?