The Shining and several other Kubrick films are one of the few exceptions I'd make to my no-pan-and-scan rule I mentioned as it happens
Apparently after seeing such a mutilated version of his 2001 on TV Kubrick started shooting his films in full-frame (or open matte) format with the DoP composing for the widescreen theatrical ratio but protecting (i.e. watching for wayward booms, cables etc) for the 4:3 home ratio so that when the film was put on TV, video etc they wouldn't end up having to chop the film to ribbons.
As a result this means that prior to their appearance on Blu-Ray most of us have been seeing the 4:3 version of these films (i.e. Kubrick's last five, I think) and, as a result have probably got used to it.
I know it certainly hit me, if only on a subliminal level, that something seemed different when I first watched the Blu-Ray. Obviously by returning to the theatrical ratio we end up losing the top and bottom parts of the image we were previously used to seeing, which, like I say, felt odd at first. But like I say the film was composed for this ratio and after a while I could see why.
Firstly (and most importantly) having a reduced amount of vertical space arguably adds to the film's claustrophobic feel. Also, it means that anything that was missed when they were protecting for 4:3 (such as the shadow of the helicopter during the opening sequence) will no longer be visible.
Having said all this though, I could still happily watch my old video copy of The Shining anytime, seeing as it's the version of the film I was most familiar with for years. However, after watching the Blu-Ray a few times I'd have to say it takes precedent for me now, even if watching my old, slightly foggy, degrading VHS copy has its own charm once in a while