I personally, am a huge fan of the books and the movies. However, I went with a Twilight "virgin" to Eclipse last night and she enjoyed the movie very much, even without knowing any background except the absolute basics. Vampire and Human fall in love, theres some wolves, and thats about it...
Now from the "mega-fan" standpoint this was by far the best so far in the series. More action, more background stories, and more romance. My only complaint lies within the super-close up camera work the director chose for most of the scenes in the movie. It got a little annoying by the end of the 2 hours... but the Cullens did look amazing. Action/Chroreography was a million times better. Even if you've tried the Twilight Saga and weren't impressed this movie is worth watching.