A huge part of why I love this museum so much is that at times it feels old-fashioned. Most science museums now have all these flashy interactive exhibits designed to try and get kids intereseted in science, but most of the time half the interactive features are broken or there's a line to see them and some bratty kid keeps pushing ahead in the line even though it's your turn to stand in the middle of the bubble tunnel.
Though I would never call NHM out of date, I love the old-fashioned way they have of displaying things sometimes. The gem and mineral room is a perfect example of this. It's a room full of cool rocks that doesn't try to be anything more than a room full of cool rocks.