I've got this one and it is brilliant - very small, light, and the sound quality is fantastic. I'm actually in a band and have used it to record a few demos too
It depends how professionally you want to go. I have a Zoon H4n which is around £260 but records excellent quality sounds.
There are some examples on this Audioboo account from someone who has taken it out top record ambient noises and also for live music and interviews. So that should give you an idea of the quality.