No there is definitely a problem with the newest safari and OS X. The web page is sluggish and produces warnings like "this page is using a ton of energy, closing it will improve the responsiveness of your Mac". 

 

Composing posts can sometimes be ok but most of the time, the editor will grind to a halt where you have to wait to see the response of the cursor when you hit a key. Something is eating up a ton of overhead and it's recent.

 

Wiggling