Far from the best, but also not the worst. Corsair have recently released some better quality CX units, but I don't believe the 750 version is one of them.
The CX750M Typically don't last too long. Couple of years if you're lucky.
Much better off investing in a quality PSU from the outset. Refer here:
http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html
Tier 1 or 2 is what you're looking for. All quality units with proven longevity.
As an FYI - if you haven't yet purchased any components, you might want to gather some feedback here regarding all your components, not just the PSU.
There's few tasks where the 8320 would be the recommended solution.
Budget & planned uses would be helpful.