Johanna's place was perfect. The location was amazing, Johanna was kind and flexible, and the apartment had everything I needed for my 2+ week stay.
I was super happy with the location. I debated staying in the 11ème for part of the time for the food scene, but don't regret not doing so. Johanna's place is extremely central, and the Réamur-Sebastapol metro is about a two minute walk away for the times when I couldn't walk somewhere. The apartment is in a lovely little square with a church across from it, and everything you could possibly need within one block. There's an amazing new wave coffee shop around the corner—maybe the best cappuccino I've ever had—and a Monoprix next to the metro stop for groceries and anything you forgot to pack.
The apartment itself is HUGE and very comfortable. Hot shower, comfortable bed, and fantastic afternoon light. I worked from home in the afternoons/evenings. The only thing to note is that the internet was a bit slow, which wasn't ideal for VCs (upload speeds of about 0.5mbps). However, I am probably the only person crazy enough to go to Paris just to work remotely, so for most people it's probably fine. I had no issues with normal internet activities or Netflix, and just used my phone as a hotspot for work.
I really hope to be back again someday, and would stay here again in a second!