The good: Amazing location right in the middle of St. Germaine in a very quiet street with a lovely green outlook and a view of the Eiffel Tower.

The not so good: It is tiny! But, to be fair there is still enough room for two people and for the price and location it shouldn't be too much of a deterrent.
The 75 steps to the apartment (but a good excuse to enjoy the amazing French food)
The toilet is external and shared - not far away and NOT downstairs, but not in the apartment itself. I didnt see anyone else using it but I did wake up one morning to discover their was no toilet paper (not so trivial when the shop is a few minutes away and you need to get up and down the stairs).

The bad: Unfortunately my visit coincided with a bit of a heat wave and, being an attic apartment it was STINKING hot and there was little relief from the fan. Had the temperature had been a little bit more mild this would not have been an issue.

Overall a good and relatively affordable place to stay right in the heart of Paris.