Delightful premise, delightfully developed, this show is lovely escapist comedy.
It's a brilliant mash-up of paranormal, historical situation-based comedy with a wonderful cast. Imagine a Ryan Murphy series, but instead of being murderous and terrifying the ghosts from various centuries exist as stir-crazy kooky roommates who, with only the slimmest ability to interact with physical reality, pass the time playing charades and performing skits. Toss in a sweet young contemporary married couple, one of whom gains the ability to interact with the ghosts...and hilarity ensues.
The more of this show I see, the more I love it - can't wait for Season 4!
One aspect of this series that I adore is that they don't spend much (if any) time rehashing the setup: the characters reveal depth and complexity and develop as the series progresses, albeit in comedic ways.