"OS X Yosemite has added yet another wrinkle for third-party SSD users, as the new kext signing security measure included in the new operating system means that Yosemite systems will refuse to load modified drivers such as those used by TRIM-enabling software."
Google "Yosemite non-Apple SSD"
see -
https://www.cindori.org/trim-enabler-and-yosemite/
Disabling kext-signing globally in your NVRAM/PRAM seems to be the only solution. This is not optimal but we most of us got on quite well without kext-signing in Mavericks, so it ain't fatal. Just remember that resetting NVRAM/PRAM will re-enable kext-signing and initially you won't be able to boot until you have re-disabled it.
I think Apple are very unlikely to remedy this - it isn't their style.
Mac (who added a Samsung Pro SSD to his MacMini and can't be arsed to go through the relatively simple contortions necessary to upgrade to to Yosemite)
