If there's one thing to take away from the NTE experience, it's that we've never given Sonic Team enough credit for what they accomplished with PSOv1. We often give them a hard time for V1 being so buggy and unfinished, but the NTE was compiled on October 25 of 2000, and JPv1 was compiled on December 6. Considering how unfinished the NTE is, ST must have been working really hard during that last six weeks to finish the game. I'm going to try to note every single difference that I can, so I'll separate them by topic. Some of these observations have already been made by other people, but I wanted to make a somewhat comprehensive list. The differences in this list are made in comparison to V1; for each item in this list, if I don't state how a particular behaviour changed in the final game, you can assume that V1 has the opposite behaviour of how a particular feature behaves in the NTE (assuming you don't already know what the behaviour is in V1). Here we go...
Starting the Game
Of course, one of the greatest mysteries surrounding the NTE is the question of whether Forest and Cave are all that the disc contains. As Treamcaster discovered, it's possible to get into Mine 1, but is there anything to do there, and even if there is, what about Ruins? Furthermore, if the other areas exist, then why did Sega try to hide them? I took a peek at the disc's files, and lo and behold, the NTE contains files for Mine 1, Mine 2, Ruins 1, Ruins 2, and Ruins 3. Still, the question remained: are the areas playable? After a bit of tinkering, I discovered the answer: Yes.
Mine and Ruins are fully playable in the NTE! The areas are less finished than Forest and Cave, which is probably why Sega didn't allow people to play them (that, and the purpose of the NTE was reportedly to test the server load moreso than the game itself, so Sega wasn't really looking for any opinions of the game, since they were well aware that it wasn't finished yet and probably wanted the final levels to remain secret until launch day). After a bit of tinkering to unlock Mine and Ruins, I spent over four hours documenting these areas and how they differ from the final game, too.
Are you ready for round 2? OK, then let's get started!
Of course, none of the Mine and Ruins content really reflects what Sega wanted people to see in the NTE, so it's not exactly "official" to use these areas or fair to judge Sega for content that they didn't even intend for us to play. Even so, it provides a fascinating look at how PSO's development was progressing a few months before the final game came out and gives us some insight into some of the ideas Sega shelved until future releases or scrapped entirely, as well as some of the things they wanted to do graphically but decided the Dreamcast hardware was too weak to handle.
Finally, the NTE works perfectly with GDEMU, which is also the reason why I was able to bring this Mine and Ruins information to you.
That, folks, is what I've learned about the Network Trial Edition in the ~15 hours I've spent playing it so far. I hope it was interesting.