Looking at how they started out of the gate (May and June 2013 reveals), and all the negative publicity they have attracted, it is a miracle that the XBox is where it is at now.
Lots of credit needs to be given to MS and Xbox management for having the vision and courage to quickly do 180s on all unpopular policies, lots of credit has to go to Phil Spencer for having the guts to marginalize Kinect which ate a lot of investment but ended up being their albatross, lots of credit goes to their marketing department, and lots of credit has to go to the games division that is trying to produce quality games.
When they started last year, I was upset and disappointed, and I wished them to fail miserably. But now, after 15 months on a market, XOne is definitely not a failure.
Cannot really say it is a huge success either - it is just doing very good, and has become a marketable product able to compete with PS4 at a decent, dignified level.