Update: You can now safely enable Trim on OS X with Disk Sensei:
Safely enable Trim on Yosemite and El Capitan
In Mac OS X 10.11 El Capitan, Apple has done a full 180 and opened up parts of their driver that allows access to Trim functionality.
This is great news for Mac users around the world that are using 3rd party SSD’s. In Yosemite, we had to deal with lifting a lot of security features in order to benefit from Trim.
With this new driver functionality, we can enable Trim in El Cap (and upcoming Yosemite 10.10.4) without risking the issues with gray boot screen.
Updates are coming soon to Trim Enabler and Disk Sensei to take advantage of the Apple sanctioned way of enabling Trim. We’re finally going to get Trim on the Mac without compromising system security or stability.