A really great place to visit with kids (when I visited mine were 11 and almost 9, both science museum veterans). A lot of variety of displays to look at, mirrors to pose in front of and enjoy the cool effects, puzzles to work out, electricity, bubbles, etc etc. Very interactive and a lot of fun - would suit both those inclined to sit and read and those who are too impatient for anything that doesn't involve being active. Also a really nice change from sightseeing, and can break up a holiday nicely.
Only negative was lack of food available - we had assumed there would be a cafe but there was not so had to wait until going across to the History Museum to eat - so definitely worth taking snacks or at least making sure you eat before - although it is a sign of how great it is that my kids had not had breakfast before (as planned to eat there) and still lasted 4.5 hours!
Would definitely recommend timing your visit for a less busy time - in our case we visited first thing on a Sunday - for the first few hours it was very quiet and we were able to do almost everything without waiting (or when waiting, just a minute or two), enjoy the mirrors alone (recommend doing this first as makes for some great photos) etc - in the last hour or two it was noticeably more crowded, but we were still able to find lots to do, and get to everything in the electricity display.