finder is very slow to show files in yosemite 10.10.3
I also faced a very, very slow Finder. After looking around on the Internet I just started trying different things.

This worked for me:


Make sure you have a backup using Time Machine (I did not need it, but you better do it in case...).
Open Disk Utility and check the Macintosh.
It showed different problems in my case, and wasn't able to repair it using Disk Utility. Therefore follow the next steps.
Restart your laptop holding cmd+R until the Apple logo appears.
Choose to repair the disk.