Part 1: First impressions.
First off, before Tenebra's release the last time I opened FSO was for WiH Acts1/2 and Vassago's Dirge. So it's been a long while. I had to reconfigure my installation, setup the command lines again, and build a whole new pilot file with my keys rebound (because I play with a mouse and despise the defaults). That took some doing, but its relevant to what I'm going to say. For reference, I'm playing on medium difficulty.
Without a doubt, this campaign has the highest difficulty spike of any FSO mod I've played yet. It didn't help that I was rusty, but the new gameplay mechanics weren't so much introduced as thrown in the player's lap with a "here, you'll figure it out eventually." Now, I like games where you have to learn new skills over time, but some introduction would be nice. I think the problem here is the development team played these missions so many times they didn't ever really get a feel for what it would be like for a player approaching them for the first time. Replaying a mission once or twice after your first run through it is fairly common and expected. Replaying a mission 5 or 6 or 7 times because it took you 3 tries to even figure out what was going on in the first place is highly frustrating. FSO's lack of a quicksave makes this doubly irritating as a minor mistake late in a mission after doing everything else flawlessly leads to mission failed. When you see that for the 6th time, it doesn't make you want to do better, it makes you want to quit. And while I could have switched to very easy, the mission failed I was getting wasn't necessarily because I was getting blown to pieces, so it wouldn't have really helped. I've put this point first because it's my greatest actual criticism and it's all better from here.
Next: briefings. These tie into difficulty because the briefings were - generally speaking - clear as mud. It's a good thing you had the sense to summarize them all on the last pane, because that's the only place I got a real sense of what I was going to be doing in the mission. Which brings me to the next point...
...the dreamscape. What a fantastic idea and what a wasted opportunity. I really enjoyed the concept, the map, the conversations, but every single time I got out of the dreamscape and went into one of the infernal actual mission briefings I thought: why the hell didn't they model this complex mission briefing in the dreamscape?! Part of the difficulty was the need to replay the mission multiple times to get a feel for the layout of the complexity of the engagement zone (more on this later), and the dreamscape would have been the perfect place to show the superior tactical origins of the Fedayeen by modelling those engagements zones in the dreamscape and giving you the briefing there. Yes, it would have been a lot of work but the payoff would have been pretty frickin' awesome. So yes, while I thought the dreamscape was a fantastic addition to the campaign, I also thought it was underutilized, especially given how dense the mission briefings were.
Now, onto the mission design. I have to hand it to you folks, these missions are unique in FreeSpace because of their complexity, the complexity of the layout, and the immersiveness of the environments. They were also OVERWHELMING, which is why I really wish you had used the dreamscape to better potential, because it would have let us appreciate the tactical puzzle of each mission without replaying it half-a-dozen times (frustration factor). The missions were extremely well done, if difficult, but once you got the feel for being an operator instead of just a combat pilot, they get very interesting indeed. The only problem is that it can be difficult to really explore your various options in the time sequences allotted. I realize you don't want to hand-hold the player and reveal everything, but you've strayed too far into "figure it out!" mode. Again, another reason why the dreamscape would have been such an ideal location for the briefings to occur.
Last: keybinds. For those of us with non-standard layouts and not all the keys bound, it is very irritating having to revert to a default layout and load the mission just to figure out what key I should be binding. I would strongly suggest you either list the actual key commands we need in the mission briefing, or an "ensure these commands are bound before playing" in the readme/install instructions. Also, instructions like "Alt-J To Jump" or "Alt-X" to change missiles are not helpful for rebound keys, unless you tell players to rebind them to certain commands. It's a common annoyance of mine in some FSO mods that designers assume default binds when there are ways around it.
All in all I think Tenebra is a monumental achievement in modding for FSO, but I do feel like there were some missed opportunities here and the difficulty curve made it unnecessarily frustrating. The story and gameplay complexity is second to none, however, and it brings new innovation and life to a canonical Freespace storyline.
