Like map25, this level is extremely tight on ammo. In fact, the monster health to ammo ratio is worse on HMP than on the earlier level.
On the other hand, this map doesn't suck. It's my least favorite of Sphagne's levels in the wad, but it lacks the egregious stupidity of map25 in its physical design. Nowhere in map27 am I stuck at the top of a high cliff, while monsters swarm at the bottom, ready to rip me apart with their infinitely high claw attacks if I try to jump off.
What there is instead is a reasonably enjoyable level in the "stretch your resources as far as possible" vein. This is helped by the presence of three berserk packs on the level.
The map has a low-key opening in a city-like environment. In Sphagne's usual style, this is fairly sparsely detailed, and comes across as a bit blocky and bland. Once you enter the building at the centre, however, things pick up both visually and in terms of the action. I enjoyed the platform hopping sections here. Not sure the soulsphere and mega armor really deserved to tbe tagged as secrets, but I'll take them.
Things pick up once you've got the blue key, with a 'marina' section that features tougher monsters, and ultimately leads to the final section of the map. This fortress, surrounded by lava, is no easy place to storm. Monsters of all variety abound, with chaingunners being especially troublesome as they snipe you from all angles.
Eventually you get inside, and face the end game. I declined to fight Mr Cyberdemon, preferring to lure him away from an elevator and then ride it onward through the level. I managed to exit with about 70 bullets and 20 shells, IIRC.
This 'scrimp and save your ammo' style is definitely not my favorite kind of challenge in a Doom level, but this is a pretty well-executed example of the type. You get berserk packs, and a decent number of demons and spectres to use them on, plus plenty of opportunities to create infighting if you choose to use them.