The big advantage of stereo vision is that it allows an individual to perceive far more about their environment than without it. One physically sees more, and one is able to judge distances and shapes far better. It is for these reasons that real 3D films have been a tantalising prospect for many decades, long after stereo photography became popular.
Over the past years I have had the chance to watch a number of 3D films, both truly filmed in 3D (Avatar) and later added with post-processing (2010's Alice in Wonderland). Even for films which were shot in 3D a number of large obstacles remain before they'll come close to a true 3D experience, such as that for example offered by Virtual Reality (VR) technology.
One of the main sticking points with 3D films has for a long time been the framerate, or lack thereof. Comparing the usual 24 frames-per-second (FPS) 3D films with the (much rarer) 48 FPS films, one can see that the latter is much smoother and more pleasant to look at, especially with panning or fast action scenes.
A few days ago I went to see my most recent 3D film, Doctor Strange, together with a bunch of friends. At this cinema they used a non-IMAX screen with active glasses, meaning not using polarised frames. Theoretically this makes for the best possible experience, as there will not be any overlap of frames per eye and not having the darkening effect of the polarisation.
The main issue with films trying to be 3D is that since they are filmed using lenses, they always have a focal point, effectively meaning a point that's in-focus in the scene while the rest is blurred. This is very disconcerting while looking around the scene as it feels as if one's vision isn't working normally. It also makes that every object that's not in focus (especially nearby objects) turns into a shapeless blob which one's mind cannot make heads or tails of.
Basically this means that you're not free to just look anywhere in the frame, but are forced to follow the focus of the camera. This is different from VR, where every part of the visible scene is in focus when you look at it. The resulting effect is of a scene which looks partially 3D and partially just like (blurry) 2D cut-outs.
One could say that this is no different from a 2D film, but the difference there is that the brain interprets a 2D image very differently from a stereoscopic one. With the former there's no expectation of it being a scene one can look around in, as it's just a flat image in which we can recognise shapes. With the latter the expectation is that it's just like our normal stereoscopic vision, but the limitations make that this is left unmet.
My personal experience is that of an experience markedly worse than the 3D effect experienced with VR and Nintendo's 3DS console. Some parts of scenes are cool due to the added 3D effect, but this is mostly when the camera has finally stopped moving and we get to focus on a close-up scene. Sadly such scenes are rare and in general I don't really feel that one misses a lot by watching it in 2D format.
Now if the FPS got upped to something reasonable (60+ FPS per eye?), and everything in the scene was in focus, then it would work. What we end up with today is kind of somewhat okay-ish at best, but nothing mind-blowing.
Especially after exposure to VR my feelings about current 3D films is that they're essentially a gimmick without a lot of added value.
Now VR... there's a topic which is truly mind-blowing. Part of me thinks that eventually VR will replace films as we know them today. I really hope it will and take films properly into the next dimension.