I've been loving having access to the extended catalogue that Spotify offers. But I'd also been feeling somewhat ripped off as the music sounded life-less. What I was hearing was bass-pumping of a really bad compressor and smashed transients. It took me a while to get my head around that this was due to the normalisation feature of the player pushing the levels into a (shit) limiter.
Ian over at production advice explains this far better than I can. In short, Spotify have implemented a rather crappy non-musical limiter in their player to deal with inter-sample peaks. I think this is probably a sensible move on their part, but I wish they would put some effort into making the limiter a bit more transparent. Even better would be to introduce a "hi-fi" option in the decoder which drops the level by 1dB. This would also make the inter-sample peaks not matter.
Now that I've worked this out I'm actually enjoying listening to Spotify. I've just got to get used to the level of some tracks being louder than others.