I had a siamese who wanted to be an only cat and who used to express his need in unsavoury ways (peed on my face when I lay down...)
Eeeeew! And I thought it was bad when I came back from voluntary work at an animal rescue and my oldest tom didn't like the "smells" so peed on my knee! (My friend, however, thought it was hysterical
)
As far as I can tell, my cats are pretty content in general. But The Old Girls senility makes her a bit confused and disorientated, so she has little outbursts of crying. Sometimes she sounds so sad it's just horrible.
With regards to the feliway, the only thing that concerns me is that it may affect the others, who are perfectly happy. I don't want all my cats to be like zombies because I feel the feliway is necessary for one of them.