The area of L'Opera itself is central and a nice area with boutique shops, Galleries Lafayette and nice restaurants. I stayed there in the Intercon some years ago and loved it. A lot of the major sites are walkable (e.g. Notre Dame, Louvre, Champs Elysees) but not a short stroll by any stretch of the imagination, my advice would be plan a walking route one way then take the Metro back.
I see this is only a 90 room hotel too, given that most Paris properties are high categories would expect a very high rating for this one.