Even after playing many of the well known more modern wads this is still my favorite megawad.
I've played through the entire megawad in both gzdoom and crispy doom.
So far I've only been able to finish it on UV once due to its high difficulty level (although I've come pretty close to doing it again)
The maps are highly details with overall good layouts and architecture. (However some of the larger maps are quite confusing without the automap.
The wad inherits many features from the original iwad such as the intricate monster placements and common use of traps. Many of the maps are directly inspired by maps from plutonia and even doom 2. The music is very well composed and does a good job at complimenting the map.
Most maps in the megawad give a good supply of health between encounters which helps stop the maps from dragging out. Ammo can be semi-scarce on some levels but can still be beaten without running out of ammo even without infighting. Enemy encounters are set up so that the levels always keep the player on their toes, while still giving out enough supplies so that the maps don't be become too unfair. A lot of maps will also start with several enemies creating a fast paced experience.
Overall, plutonia 2 is one of the best megawads I've ever played and definitely my personal favorite.
Favorite map: map 09