cons:
If you typically adjust your thermostat when you're out of the house to save money, you won't be able to during summer/winter.
more wear and tear on your house
you'll need more 'stuff' at your house -- high chair, toys, diapers, etc.
pros:
your child gets to nap in his/her bed
no need to pack up your child every morning (particularly nice if your child ever sleeps in)
no need to drive somewhere to pick up child at the end of the day