While it does a better job at pointing out the Doom engine's flaws, theres a very fun time to be had in Hexen.
The Story in Hexen takes place at around the same exact time as Heretic, only it takes place in a different kingdom. In Heretic, The land of Parthoras was taken over by one of the 3 serpent riders, D'sparil, and was later then freed by a Sidhe Elf named Corvus. In Hexen, the kingdom of... well, Hexen, is overshadowed by the second serpent rider, Korax, and 3 heroes: a Warrior, a Cleric, and a Mage go on an epic quest to free the land of Hexen from Korax's minions. The story is very motivating, and it adds on to the lasting value of the game.
The gameplay is a major step up from the standard Doom and Heretic formula. Instead of having about 30 or so "levels" to go through, collecting keys and all, Hexen uses a "hub" system, which involves passing through groups of levels that are connected to eachother, in which the player has to solve a series of puzzles by traveling back and forth between the levels instead of going through a series of linear ones.
The difficulty of the game is varied by the choosing of one of the 3 different classes in the game (Warrior, Mage, Cleric) and depending on what strengths and weaknesses you choose based on your class, certain elements of the puzzles in the game will have different difficulty levels, as is with most RPG's.
The graphics in Hexen utilize the Doom engine to it's absolute fullest potential. There is lots of atmospheric level design, and even in this day in age, Hexen still feels so real to the core, even if the trees DO look like paper :D. The game may not have bump-mapping textures like Doom 3, or high polygon count like Gears of War, but the game has lots of neat effects and a high level of detail such as Blowing leaves, Lots of mushrooms in swamp areas, and even fog effects, and other effects that few FPS's have today.
There are several versions of Hexen. It is available for the PC, the N64, and the Sega Saturn. I have tested the PC and N64 games out, and they are almost exactly the same, but the music and the graphics are different.
The PC version has signifigantly lower quality graphics and music than the N64 version, because the PC version uses synthesized MIDI music and the textures and sprites are very pixelated. The N64 version has blurred textures and sprites, so the pixelation is lost and has a smoother look, but framerate problems occur almost all the time, so there are sacrifices. The music in the N64 version is nothing short of amazing. The music is CD quality, so it outmatches the MIDI music in the PC version by far.
If you have a PC copy of the game available, then I highly recommend doing a google search for something called the Doomsday Engine. The Doomsday Engine is a utility that gives Hexen smooth textures and sprites, dynamic lights, and other graphical tweaks. There is also a Hexen N64 "music pack" that updates the PC Hexen's music files to the N64 version's music, so you can enjoy the superiority of the N64 game right on your PC. All you need is the HEXEN.WAD file and you should be ready to give it a try!
Ok, the value. This game has a very good amount of content in it. There are about 5 or six hubs in the game, and each of these hubs contains about 4-6 different levels within it. This game will take the average player about 20-25 hours to beat.
Now, on to the cons. As I've said before, due to the engine this game runs on, There are some flaws that the game has. for example: No matter what weapon you are using, even if it's your own fists, if you swing it through the air, EVERY monster in the area will go on full alert. This is because in Doom, you're usually in tight corridors, so any sound you make will be heard by the zombies\demons close by. The Doom engine was unfortunately not updated to having LARGE environments. There are other situations such as this that I can't really explain, but I think you get the picture.
Overall, Hexen is a great game, and It's lasting value has lived on 'till this day, and that's saying something.