My cats go crazy when we place down a newly-cleaned, freshly-filled water fountain. That is, after they gather around and watch us clean and fill it. And then they race to lap up the first drink. It's like when we clean the litter boxes: They gather 'round and watch, anxiously waiting to release upon the fresh litter.
They like fresh and clean ... also, I think they're super nosy when we're messing with their "stuff."