10.10.4 adds the trimforce Terminal command, allowing users of third-party SSD boot drives to enable/disable TRIM support without the need for helper apps like TRIM Enabler. I personally strongly discourage people enabling TRIM on non-Apple drives for a variety of reason, but if you are so inclined I’d recommend performing a full backup of the SSD drive first, and then maintain a regular backup strategy afterwards. The Terminal command to enable TRIM is: sudo trimforce enable

Warning: After executing this Terminal command, it may take several minutes for it to complete, and Terminal app will appear to have hung. Do not shut down/reboot your Mac until you receive the prompt “Operation succeeded. Your system will reboot momentarily, please wait…”, otherwise you may brick your SSD drive.