The ipod shuffle is a no frills mp3 player. It has no screen and is very basic. The reason for its higher price is obviously the brand name! It is useful in that it clips anywhere, so its ideal to go for a run or down the gym or even doing the housework.
Its small, light and compact. The battery life is very good because its very basic. Its straight forward to use, and you do not need to use itunes with this which does complicate things sometimes!
They are quite expensive for what they are, you can get a less known brand name for the same price with a lot more features. But you are paying for the Apple brand and they are do make high quality technology. It will always be the most popular option.
I have never had any problems with my shuffle, unlike other mp3 players and so far I've had this model about 4 years now.