I like them when they feel natural.... like where she's conveying emotion without words. Being that I listen mostly to music whose language I don't understand, these don't bother me at all
But when she sounds like she's forcing out the la la la's or whatever (like in newer versions of "Who..." - I felt the original's "lala"s and "aah"s were VERY effective, but every re-recording or live performance since 2001 has had them feel forced), well then I don't buy it and I don't like it.
As for when they're actual words like "yeah" and "no," I think they're fine. They're good confirmations & strong denials.
They get kinda repetitive at times (like "Sparkle"'s "no no no"), but if the song surrounding them is really good, I overlook it very easily.