I am having the same problem, i upgraded to 10.9.4 on my iMac with the following configuration
27" Mid 2010
Processor 2.93 GHz Intel Core i7
Memory 16 GB 1333 MHz DDR3
Graphics ATI Radeon HD 5750 1024 MB
Software OS X 10.9.4 (13E28)
And I am not running any spectacular software at the moment that would cause any different behavior than before, I have Sophos Virus protection and little snitch running to monitor the network traffic.
I have been using chrome for the last couple of years so please dont tell me that its my software or any other made up blah blah blah..
Lets be clear the only changes that I have made is the upgrade to 10.9.4 about 5 hours ago, now here are the issues that I am facing.
1. Fan is on constantly
2. Finder works at a snails pace and some applications that access the drives seem to either not be opening or opening so slow that it is unbearable.
3. Overall system seems to be slow and hard to work with.
Any suggestions or simple help would be greatly appreciated..
Thanks everyone..