My girlfriend and I were very happy staying at Ju & Ch's place for a few nights. It's within walking distance of most of Paris or if not, you've got a bunch of different metro stations to choose from within a few minutes of the apartment. It's also less than 20 minutes from Gare du Nord on foot.
The place is small/cosy, but comfortable and I personally didn't have any problem working from the apartment for the few days I was there (wifi was around 40Mbps). I thought it good value for money.
Ju & Ch were both super hosts, very responsive and helpful, getting back to us within less than an hour on any manner of questions.