Technically I've only read the book myself once since the first time my father read it to me when I was young. Normally, when I reread books or rewatch things, that is indeed the case. I notice different things, details, characters that I hadn't the previous (especially the first) time(s). It's fun and usually makes me like a book/series/film even more.
But in the case of WSD it had been so long I could hardly remember anything at all anyway. I simply remembered I liked it a lot (my father said I kept begging him to read more each evening so I guess I enjoyed it a lot^^)
Same with the series, watched as a kid on tv a lot and only rewatched it about 1,5 to 2 years ago now? I did remember (or rather recognize) more of the series though than the book, probably since I had seen it more often as a kid (yay for reruns?). Except S3 which was new to me. Didn't even know there was a S3 before.
I do wish I could remember who my favourite characters used to be as a kid. Because considering I had completely forgotten Vervain even existed, I doubt it was him!
Also I do plan on rereading WSD this year. Enough time has passed for it to be a 'fresh' enough experience again and really it's just too good not to. Besides I want to do it before the mini-series which I believe is scheduled for late this year (unless that's changed again).