I saw this when it came out on TV, but didn't tape it then, and always wanted to see it again. I finally did only recently. I found that it held up very well, and now I would love to have it on DVD. It certainly has its flaws, for example, the made-for-TV budget is obvious, but the story is interesting, and the actors, first and foremost John Hurt, are engaging enough to make it stand out.
Who cares if the idea isn't completely new - which story is? LITTLE SWEETHEART is much more modern and suspenseful than BAD SEED (for example, the adult characters contribute more to the plot, and there is less analysis and moralism). Furthermore, I find the comparisons with LOLITA highly problematic: in contrast to Humbert Humbert, there is no reason to assume that Robert Burger (Hurt's character) has any paedophilic notions. If some people find the film fascinating in this way, I wonder how much is due to the film's portrayal of the girls, whether deliberate or not, and how much in the eye of the beholder. In any case, this is putting the film in the wrong category, at least in terms of subject matter.