[susan53]

It depends on what type of adjective is used.

Take an adjective like hot. It's a gradable adjective - that is, something can be a bit hot, or very hot. If you use quite with a gradable adjective then it will probably have fall-rise intonation and have the meaning "somewhere between a bit and very", and it may be used with negative or positive ideas.

When I first read Michelle's message I wondered if the explanation of rather = disapproval might be right too, but looking in a concordancer, it's not true of many of the examples. This was the first one that came up :

... and their supporters are rather polite about it, often much more so than ....

Quite also has a different meaning though when it's used with non-gradable adjective. If you say I'm quite certain (falling intonation on quite this time) then it means completely, absolutely. Rather can't be used in this way or with this type of adjective.