my favorite part of this map is the entire first half. The main player path through the level seemed linear but there are so many side areas, secret ledges, and so on that I spent most of my time jumping around, looking at different platforms and figuring out how to get there. In your readme you say the secrets aren't satisfying (due to the items they contain) but I think the satisfaction of finding them is good enough.
Your maps have all had good secrets, but I think what i especially like about these ledge-hunting secrets is that the player understands the rules of the game physics, so when looking around, you are using that understanding to judge the geometry you're looking at for it's climbability/jumpability. Other classes of quake secrets are commonly "shoot the unmarked button" type secrets where it is less about players applying their knowledge and more about random experimentation and luck.
One small negative I think is that for a first-time player, the different ledges and vertical "trunks" of the level all looked pretty similar. This alone would have been okay but then whenever i used a teleporter to get back up from a secret I completely lost my sense of orientation. There was a particular secret (blue armor i think) where every time i saw it from below, i could see how to get there, but after teleporting up i had no idea which direction that ledge was.
The final arena battle is very well done, good combat pacing and visual spectacle. Giving the players buttons to start each wave was a nice touch, it allows the player to control the pacing but not in a way that makes it too easy (since each wave was a pretty strong combat.) I am not a huge fan of these arena battles since so many maps seem to have them and the gameplay is always pretty similar, but like i said, it was still done.
Visually the level was very distinctive, the brushwork plus the overall structural shape of the level. It seemed that it might be inspured by
Lun3DM5, but also didn't seem in any way to be a clone of that, just the general feeling of clusters of cubes with "ambient occlusion"-type lighting.
The translucent energy bridges were a nice addition as well. Good technique of training the player in the start map (though the first bridge in the main map is right in front of the player so that could have served the same purpose.) Also in the start map it took me about a minute to see the button. All the red runes looked much more noticable! Anyway, I managed to kill an NPC by turning off the bridge he was on, that was another nice emergent moment that didn't feel contrived.
Bobs were used well, the wide open sky was a good place to put them on big patrol paths and randomize how the player encountered them. I think what I have disliked about bobs in the past is how they were placed -- in super tight hallways where I can't dodge, in groups when I am underpowered, and sometimes at a distance where their small bounding box makes my SSG useless! In this case when i have a nailgun and they are usually solo, they felt pretty good.
Someone else said, sometimes they were in a tight place and wanted to be out in the open, other times they were in the open and they rushed for cover. That was a good feature of this map's combat. The small ledge with a Pyro on it was an example of this.