Every character in FFIX at least has some good use throughout parts of the game. It's not as if one dreads having to use them as the story progresses.
Quina is very good through the first half of the game. Whenever she has to be in your party, one can make good use of things like the 'millionaire' ability and her blue magic.
She does become a bit obsolete through the second half. Freya is a strong player through the first half as well, but starts to lack later on.
The great thing baout this is that the developers were well aware of this and so when you are forced to use them, it is rather fun. You won't have to use Quina or Freya much as the game makes them less usuable.

However, if one wanted to, they could very well do so and still kick some ass.IX was very well developed.
Freya is a semi-popular character to use, actually. My strategy just doesn't work with her (never been a fan of dragoons).

Some say Amarant isn't good, but in my opinion, he is a must if one really wants to go all the way and max out. Healers will eventually become obsolete because of auto-regen, auto-life, etc. and Amarant has abilities that fill in the gaps, like revive. Since he is also really quick, he makes for a good support character. To boot, he hits pretty hard as well.