Safari is slow, slow, SLOW!

Works fine for me

No problems here.

I've found on every computer I've tried that Safari on Yosemite is noticeably quicker and more responsive than on Mavericks. Especially in terms of scrolling smoothness, and page load

Mine was super fast but this last week something has happened and pages stop responding or take forever. Sometimes I have to reload or quit Safari.

While I don't want to turn this into a "which browser" thread...

If there is an application you use on your computer that is not performing as well as you'd like it...there is always the option to try alternatives. While I understand your initial goal was to "debug" what is causing your specific Safari issues, since yes, optimally Safari should run great on every machine, sometimes this is a long road to go down.

So, that being said, why don't you give another browser a try. For a day, a week...see if you like it. Google Chrome is an outstanding browser. It's the browser I use, recommend to others, and is the browser of choice for almost every person I know that is "into" technology. There has to be some reason here

Sure, it's not exactly the same as Safari but maybe it will alleviate some of your issue and you will find you have an issue free browsing experience. Let me know what you find.

Sounds like somethings wrong. Safari under 10.10 is faster than ever on my MacBook Air (mid 2013).

For me, Safari works reasonably fast under Yosemite. However, I do on line courses and Safari can't handle the pages while some of the more common browsers did just fine. In the past I have found similar situations where for some reason Safari seems unable to deal with certain web pages either quickly or successfully.

On another note, perhaps the OP should consider reading some tips on optimizing Safari including more common items including how often to empty history and deal with cookies and other items that can impact performance.

Safari in Yosemite is dramatically better on my '08 MacBook than Mavericks ever was.

I found that everything is super fast apart from opening new tabs and adjusting window size while playing videos on YouTube. Try rapidly doing cmd+t, compared to doing it in e.g. Firefox. Love the speed of it otherwise though.

Yosemite on late 2013 rmbp.