Everything is in the title! It is very convenient to have these 4 USB ports that come directly to the office, rather than having to bend down to plug in a USB drive or other device. The fact that you can choose to connect it to the mains is obviously more in terms of performance. A small LED indicates the status of the connection: blue if it is self-powered, green if connected to mains. I would not speak of the special outlet to charge faster devices, I'm not in the utility, so I do not use it.
Finally, it is discreet and classy. Black gloss top, matte black underside and rounded curves. Small rubber feet underneath to help provide grip with the medium on which it is placed.
For cons, I am impressed by the size of the power unit: it is larger than the hub itself! Anyway, in my case, so it is hidden I do not really care.