murphy beds / pull down beds

I'm trying to plan out a new house I'm moving too. The current owners have a bed / desk (think sofa bed but it changes into a desk rather than a sofa). They are very expensive though and I think I'd need a deeper desk.

So I'm thinking of a horizontal murphy bed instead. There seem to be quite a few people selling them, at a range of prices depending on how posh the cupboard looks.

Does anyone have one of these or have any real life experience? This would just be for a spare bedroom so I can still use it as a study most of the time, but still have somewhere for people to stay.