We were only here for a single night as we passed through Paris. Apartment was cozy, a sort of crow's nest at the top of a quaint spiraling staircase. If you have large luggage or trouble climbing steps you might have difficulty, but we weren't bothered by it.
We enjoyed exploring Montmartre at night -- the tourist crowds seem to thin out a bit, and Abbesses actually had a lot of locals out & about.
Baptiste was very accommodating and made extra arrangements to get us keys when we arrived midday.