I've had the curved, and had 2x flat (34UM95). All apart from my current (2nd flat, which was a replacement) had obvious backlight bleed. Only this one has minimal and is barely noticeable. What they all have though is IPS glow around the corners, which shifts as you pan around the screen with your head.
Though anyone buying an IPS panel should know about IPS glow anyway so will be fully expecting this. In reality the glow is ignored very quickly by your eyes and you're more focused on the added immersion to movies and games this aspect ratio brings.
If you get one with bad backlight bleed then get it swapped, simply don't accept one with bad bleed as it's not acceptable at this price. I think I mentioned this in my series of reviews.
Personally I much prefer the non curved, in part due to having a hardware LUT, so colours are finer tuned and saved directly to the monitor when calibrated (out of box calibration is "ok", if you value accurate colours then you should buy a colorimeter...).
The factory calibration chart states it was tested with the HDMI port and the value it got. Considering these are 3440x1440 monitors, which requires the DisplayPort to be used for 60Hz, I consider that factory calibration to be a bit misleading. Moreso on the curved, as the calibrations are on a per source input basis, since it has no LUT to save directly and apply monitor wide to.