Faguswerk is not that fantastic by itself. It's a great visit, an interesting tour, you can spend several hours up to the whole day just on this WHS, but in the end the main focus for the inscription is that it is the origin of the architecture “Bauhaus” movement (another WHS of course, as well impact on Tel-Aviv building designs after the German Jews took the Bauhaus style to Israel - which some purist may tell me is not the correct way to explain it but that's the jist I got from the tour guide). Being the original is very, very huge but then it's a bit like someone telling me an old movie is great “because it was the first to use sound” but that's about it (bet you couldn't tell me which movie was first to use sound or color or 3D anyway).
There are several highlights: the entrance at the clock with its freestanding staircase, the railing near the cafeteria, the chimney, and of course the windows of the main building. Very worthy of inscription and a huge impact onto the world of architecture.
Keep in mind that to see the inside of the factory you must join a tour that runs on weekends (the factory is still in use so it's offlimits otherwise), but the website has a clear indication of special holiday times. Then again, if you can't go on a tour you can take a video guided tour on your own in several languages and you get a lot of information already, and the inside of the factory isn't as insightful as the outside. Overall the shoemaking aspect is very secondary to the visit. It is interesting that they still make the shoes in almost the same way as over a hundred years ago, it is interesting that they still have big clients and they make most of their money on some kind of fire detection system (don't take my word for it I may have misunderstood that from the guide).
The exhibition building is a long, very long museum you need several hours to get through everything, with a nice rest at the forest on the top floor as a reward (it was so empty I think most people did not make it up to that floor).
In short, you can get through this WHS for free in 10 minutes, or spend a lot of time exploring the site and the exhibition, have a cake at the cafeteria (I got sponsored $20 for mentioned that j/k but there is actually some funky design in there too).