If you look at the pictures above, you'll see that the entrance runs on the long side of the hive, paralell to the frames. A typical Langstroth hive had the entrance running across the short side at right angles to the frames. So the hive has been rotated 90 degrees so that what used to be the side, is now the front.
Advantages to a top entrance:
No problems with the skunks.
No problems with the mice.
No problems from not mowing the grass. On a bottom entrance the tall grass can severely limit traffic in the hive.
No problems from dead bees piling up in the winter and blocking the entrance.
No problems from snow piling up in the winter and blocking the entrance.
Good ventilation.
Less swarming because of less traffic and congestion in the brood nest.
Caveats:
Be sure you either dont have an excluder or there is a drone escape below (a hole at least 3/8 in diameter in the brood chamber)
A top entrance works well for ventilation with a SBB. Without the SBB you might have some ventilation problems.
Skunks were my main motivation for going to top entrances.