Well I finally updated my my 2 Mac Mini's. My only disappointment so far is the elimination of Secure Empty Trash. Why did they do that? Everything else seems fine so far.
Because SSD technology don't work in the same way that spinning disks did.
On an SSD when you overwrite a block, that block has to be erased first before it can be overwritten, and that erase operation adds a
lot of time to the write operation. Worse still, SSD blocks only have so many writes in their lifetimes.
How this works is that SSDs have embedded controllers in them, which implement something called "wear leveling" which ensures the blocks that get overwritten do so evenly. So the sequence to overwrite a block is (a) the overwritten block gets marked as erasable in the controller, then (b) the actual write operation happens at some other currently unused block, and finally as the controller's processing gets freed up, (c) a separate process is spawned to go back to the blocks marked as erasable to actually erase them.
Deletes do (a) then (c), freeing up those blocks to be used for a future (b) write.
The problem with Secure Empty Trash is that, as far as the operating system is concerned, that deleted record was already overwritten. The SSD microcontroller marked the the deleted blocks as erasable, and will eventually go back to actually erase them, but the operating system itself has no idea where those deleted blocks are/were. The SSD controller manages that completely out of sight of the OS.
So that means that Secure Empty Trash on an SSD is nothing more than a placebo, and is why it was taken out of El Capitan. Could Apple have repeatedly overwritten every empty block on the SSD? Of course, but SSDs only have so many writes in their lifetimes. That only serves to shorten the life of the SSD itself.
If you
really need to securely delete files in OS X, enable File Vault when you install the OS.