If you're looking for an apartment in a great location, you really can't do any better than this one. Very short walk to the Louvre, the D'Orsay Museum, lots of shops and restaurants, two different train lines, e.t.c. Note that the apartment is quite small, so it's definitely for two or fewer people. It'd be pretty cramped if you tried to fit any more into the apartment.
As the other reviews note, this is a walk-up apartment. I believe I counted 5 or 6 flights of stairs. If you have knee problems like I do, and/or if you're traveling with a lot of luggage, this may not be the apartment for you.
I am a software developer and I worked from the apartment for an entire week, and I can confirm that the WiFi was very fast and very reliable the entire time I was there.