Just my two cents on my latest upgrade.
at the end I bought a
Samsung 950 PRO 512GB for software and OS
Samsung 850 EVO 1TB for games.
(photos and videos still on 2TB HDD)
The biggest improvements was on the 850 EVO, games now are another story than when installed on HDD.
The 950PRO doesn't bringed any performance improvements on my rig,
before the 950 PRO I had a Corsair Force GT240GB used for the OS and Software and I see no improvements at all. Boot time are nearly identical, load software are nearly identical, working with VM are nearly identical.
950PRO is a pure waste of money, there is no real life area where this drive is faster than a normal SSD if not on benchmarks. This drive can be good on a server but this is not a server drive, for a desktop or a workstation this drive is unuseful.