This is really disappointing. I have a mid-2010 Mac Mini (the last one to have an optical drive built in) with a Core 2 Duo. Maxed it out to 8Gb ram. Even with Mavericks it ran very smoothly, and did everything I used it for (desktop stuff and light content creation). But when I installed Yosemite, it now runs like a dog. I am downgrading to Mavericks again at the weekend.
These used to be great machines, but it looks like Apple are trying to maintain their high margins by cheapening the construction of their machines. I love OSX, but I'm seriously considering a Windows machine next time, especially withe Win10 on the horizon. i even like the look of the Surface Pro 3...ahem!
Sorry, Apple, you've been making some very curious decisions lately, and you're losing customers because of it.
Biting the hand that feeds IT
