Hi, For what it's worth I will tell you my experiences. I have a 2009 iMac 27" and a 2011 MB air 13".
After upgrading to mavericks the MB air was fine! no problems at all. The iMac however was painfully slow at everything.
I read this post and tried everything here and sometimes I would think there was a slight improvement and other times there was no difference.
I tried a clean install and then restored from a time machine backup. Still running slow.
So as a last resort I reformatted my drive, installed mavericks and then added my software one at a time back on to my machine. A slow process but it also emptied my machine of software I no longer use.
The result, the machine is now working absolutely fine, running as fast sat ever did.
It took a long time for me to make the decision to do this, but was well worth it.
Good luck.