I have to disagree with John L. completely.
The N64 transfer of Hexen was great. As far as I know, the main game is functionally identical to the PC version. I am not aware of any missing characters, weapons, items, or levels from the PC original. Pleasantly surprising in and of itself, compared to most PC ports of the time, which usually had missing or redesigned levels.
Furthermore, the programmers of the N64 port actually made some very cool exclusive additions (besides the little paragraphs between levels). For example, it has a custom soundtrack remix. In my opinion, this remix is superior to the PC version.
More importantly, it has support for four player split-screen deathmatch or co-op on a single console. Hexen 64 was the first console FPS to implement this. 4P co-op was groundbreaking for the time, and a feature that is still somewhat uncommon on console FPSs today (via split-screen, or even system link for that matter). 4P co-op FPS play on one PC is nearly unheard of, and to even have 4P co-op play via LAN/Internet on Hexen PC would probably require a mod.
Also, while it is cool that they've added better lighting and 3D models to the PC version source port, it's also worth noting that these are fan-created modifications. This port was made years later than the original game, and it's not even authorized by Raven Software. Judging the N64 version's graphics by this port would be sort of like condemning the original Mac version of Marathon: Durandal because the graphics are not as good as the HD remix for Xbox Live Arcade.