Final Doom is a bizarre release. Where Master Levels for Doom II elevated fan-created levels to expansion status, Final Doom acts to fully canonise fan content by compiling two lengthy fan campaigns into an official, mainline Doom release. The ethics are pretty weird, but a charitable take is that Final Doom preserves and legitimises the creativity of the Doom fandom through its release.
As for the campaigns themselves, I found both to be enjoyable, if a little bullshit-ridden at points. TNT Evilution (great name, btw) had a wonderful sense of pacing to it, progressing through environmental phases not unlike Doom II. Despite many finding this to be the "bullshit" one, it is actually the only Doom campaign, aside from those in the original, that I never got stuck in. Perhaps I just got lucky. The Plutonia Experiment I found a little more gruelling, not just for its difficulty but for its size, but was still an enjoyable experience.
Despite my overall enjoyment, the experience of going through these campaigns was one of exhaustion. After all, they are working within the Doom II framework; there are no new enemies, mechanics, weapons etc. Each features an iteration on the same final boss as Doom II, and the original Big Bads (i.e. Cyberdemon and Spider Mastermind) are pretty played out as threats by the end. It's damn good for what it is, but what it IS is more Doom II, and a LOT more of it at that. Doom 64, also not developed by iD, is a more bold and evolutionary continuation of the series.
As for the campaigns themselves, I found both to be enjoyable, if a little bullshit-ridden at points. TNT Evilution (great name, btw) had a wonderful sense of pacing to it, progressing through environmental phases not unlike Doom II. Despite many finding this to be the "bullshit" one, it is actually the only Doom campaign, aside from those in the original, that I never got stuck in. Perhaps I just got lucky. The Plutonia Experiment I found a little more gruelling, not just for its difficulty but for its size, but was still an enjoyable experience.
Despite my overall enjoyment, the experience of going through these campaigns was one of exhaustion. After all, they are working within the Doom II framework; there are no new enemies, mechanics, weapons etc. Each features an iteration on the same final boss as Doom II, and the original Big Bads (i.e. Cyberdemon and Spider Mastermind) are pretty played out as threats by the end. It's damn good for what it is, but what it IS is more Doom II, and a LOT more of it at that. Doom 64, also not developed by iD, is a more bold and evolutionary continuation of the series.