Well this map came about from a challenge to remake E2M9 to "what it SHOULD have been". This suggestion was met with some derision, in particular the author felt it would only be a true challenge with severe restrictions.
So we have a small replacement E2M9 which tries not to exceed the object counts of the original. In actuality, there is one extra linedef, but all the other limits - sectors, things, and even vertexes, were kept*.
Anyway I think this thing turned out rather well. It is far from trivial. You have to repeatedly traverse this large structure, surrounded by lava. while constantly under threat from far-off cyberdemons on moving platforms. There is very little ammo so you end up avoiding the monsters on the structure - barons, then later a bunch of cacodemons appear from the top - more than fighting them. Lastly the structure has a lot of height variation and you are often forced to wait around for lifts.
That last part is probably the one thing that lets this map down, the repeated need to traverse the structure - often the only way to go is to teleport right back to the beginning - combined with one very slow lift at the bottom, was all just too annoying after a while. On the other hand, it's not completely overrun with monsters, and is quite doable provided you don't lose concentration. Getting 100% kills requires some effort.
Not for everyone, but give it a try if you like old school puzzle wads.
* Don't forget not to count vertexes added by node building, just the ones referenced by linedefs. Also apparently sectors were an issue until 10sectors-style sector merging was suggested.