I think that 90% of all IPS display's that come on laptops have some kind of bleed problem. For the G751's and G752's this is quite a common issue. Some are really minor while some are really bad. In my opinion, yours doesn't look so bad. I don't think it's worth returning the unit if anything else is in perfect shape. Do check for other issues also. If you find more problems then it might be a good idea to ask for a change unit.

What you see in the corners is just the IPS glow that is present on most displays. It depends on the angle at which you're looking at the monitor so you can't really do anything about that, and it's also not the manufacturer's fault. It's a compromise that you have to live with if you want an IPS screen. See here for more info if you want: http://www.tomshardware.co.uk/forum/id-1927625/ips-glow-normal.html .

But, tbh this is only noticeable in certain cases. Mostly when you have a plain black image. In dark scenes from movies or games I don't really notice it that much. But don't forget one thing, the color reproduction on this display is quite amazing (for a laptop let's say).

Personally, I'm waiting for the new laptop models that will come with OLED displays :D. Now there you'll have your black scenes as they should be.