We went here on a recommendation of a friend who has been to Prague several times before. The strange looking babies crawling up the outside of the tower were a little odd but add some thing to the some what dull exterior of the tower (what else could you do to a long grey tower?).
At about £5 to get in its a cheap visit. You go straight up in the elevator, very quickly so watch out as your ears do pop, to the top floor. The views are amazing, you can see all the way around and trying to find all the places you have been to is fun. There are sofas and some chairs along with a computer screen pointing out popular landmarks such as the Charles Bridge.
Worth a visit for the amazing views just make sure you go on a bright day.