One thing I always liked about this movie was, as someone who's also a fan of the original, it very subtly hints back to that one when they find the lab... just subtly enough to play on your memories of the old one, and by showing the gory results that could be construed as having happened after the original movie finished, gives the whole thing this terrific darker vibe.
But regardless, best scene is still easily the blood test scene. I'm a hardcore horror movie fan who's seen it all.... and the first time I saw the blood test scene, even I jumped back, which just goes to show how amazingly ****ing effective that scene really is.