All the albums that I've rated are albums I've listened to all the way through. When it comes to ratings I'd say most fall into the 4.0 category, which would be an album I enjoyed and recommended. Anything above and below that just reflects the amount that I enjoyed it above the average album or disliked it versus the average album.

5.0 are reserved for the elite
4.5 just miss out and could move up upon more listens
4.0 means it is good and I recommend it
3.5 means it is good but had a significant flaw
3.0 means it was alright, fans of the artist might enjoy

Anything below that means it is poor, 0.5 being the worst case scenario which is rare.