After owning 3 TLC 840 EVO 1TB SSDs, one of them which is an mSATA, I'd never ever buy a TLC SSD again. It's good in benchmarks, but in real world performance, even my older 840 PRO gave me better speeds, stuff like copying files, opening programs, etc. I could feel it big time.
Now when the finally awaited fix from SAMSUNG came, I quickly jumped on it, upgraded the firmware, and let it do the performance restoration. Yes, that did help, but after about 1 month, I started noticing the same slow down again.
I then sold my two 1 TB 840 EVOs and substituted them with 850 PROs.
Morale of the story: stick to MLC (in this case, the MX100)