Classic feel with fresh SP action!
Visually, the map is quite a step up from the original DM3. There is no sign of the infamous misaligned textures that plagued the original, and there are quite a few details, including computer systems, light fixtures, and buttresses to keep you aesthetically interested. The details flow nicely and create a consistant aesthetic.
Gameplay is pretty linear, but there are 6 secrets for the explorer types. While romping about, you'll come across the typical base enemies, plus some scrags, fiends, vores, and shamblers to keep you challenged. Gameplay is varied, though, with enemies popping out from behind moving wall panels, and be on the look out for ambushes and enemies attacking from above--you never know where the next attack will come from.
Ammo and health are balanced pretty well, but sometimes encounters with a shambler or a small hoard of monsters can get a little hairy, so be prepared for a challenge. But there's nothing unreasonable, and difficulty settings are implemented, so you will be fine as long as you keep your wits about you.
This is definitely a high-class map, so be sure to check it out!
Note, however, that this map requires a modified Quake engine with higher edict limits, such as DarkPlaces or FitzQuake.