Excessive edge enhancement is very ugly once spotted and once you have spotted it then you will always notice it on future films you may watch, usually you will see it on blu ray releases which use older outdated masters, sometimes the studio will take an old master and digitally remaster it, you are not always guaranteed quality when they do this because occasionally they will degrain the film which when done quickly and on the cheap often results in a loss of detail, they will try to compensate for this loss of detail by sharpening the movie, typically this is known by many outside the actual industry as edge enhancement and this is an image processing filter, it works by identifying sharp edge boundaries in the image and increases the image contrast in the area's around the edge, for example, the edge between a subject and a background of a contrasting color, you will find far too much edge enhancement on a lot of standard definition digital television broadcasts and DVD releases, your television or projectors sharpness control also adds edge enhancement to the picture. It's better to lower your sharpness control when watching high definition blu ray material, the image is already very detailed and does not require enhancement.
Now the problem with excessive edge enhancement is that it tricks the brain into thinking you are seeing more detail, unfortunately you are not, the image tends to look a lot less natural and a lot more processed, once they add this to your favourite blu ray movie it becomes irreversible, no amount of tinkering with your television/projectors settings can remove it, you are basically stuck with it, now add in the fact that some people already add excessive edge enhancement into the image because their systems sharpness control is set too high then you will begin to understand how ugly the image may become, now the degrain process is a filtering process which removes fine detail, if they kept the film grain intact then they wouldn't need to edge enhance the movie and sharpen it back up, the whole point of blu ray is that the high resolution allows for film like quality in your home, degraining a film and then adding too much edge enhancement sharpening destroys all fine detail and leaves the viewer with processed looking crap.
Typically if your screen size is large then you will notice edge halo's around people or objects, you may not realise it's an issue as you may think that's how it's supposed to look but movies are not filmed with edge halo's, you will most likely spot edge enhancement when a person is wearing a black outfit against a light background or on the wood beams of an old house, sometimes you can spot it around objects such as telephone lines or the masts of ships. Far too many movies are spoiled by this annoying "trick" that tries to make you think the image is sharp when it really isn't.
Below is an example of excessive edge enhancement, the first image is normal, the second image is sharpened, note the edge halo's you can spot this more prominently around the hand and the head and the jacket area, i have included a close up of the edge enhancement to make it easier to spot the issue. For a list of some films which contain ugly edge enhancement click here.