I enjoyed the hell out of these maps, and I'm staggered that you did them in 2.5 weeks. That you did so well in so short a time, producing, IMO, one of the most enjoyable E1 replacements I've played, is astonishing. Keep that in mind when I say that the mapset could use a little more polishing, but mostly minor stuff. The most common thing I saw was a violation of Romero's Rules For Level Design, specifically, changing floor textures without changing floor height, something I did a lot in my older maps. Sometimes you'd put a border texture between the floor textures, but more often, you did not. There were also a few (very few) vertical texture misalignments of note.
I played the maps on UV and mostly found them very easy but still with fun fights and good challenges. They are all dead easy by comparison to your cbpandemonium level, where I got killed, and am now trying to find time to attack it again. In this episode, I was seldom in serious danger, but I always had to keep alert because there were lots of monsters. I smiled when I encountered the first big trap on E1M2, right near the start. It was a good trap, but the strategy to beat it was obvious, which was a continuing theme throughout the levels. I was always happy that you weren't shy about putting large numbers of monsters in your traps, but they became fairly predictable -- press switch, and run away while the trap opens up on 2 sides, then potshot the monsters when they chase you. There was a trap on E1M2 where the walls opened up on each side of you, and as you back away, more monsters come around a corner behind you. I would have liked more of your traps to be like that, to give the player a better chance of getting killed, and greater satisfaction if they can fight their way out of it.
All that said, I did get killed in three different levels, and not surprisingly, they were my favorite levels. In the order I played them, they were E1M9, E1M6 and E1M7. I actually shouldn't have been killed in E1M9 and E1M6, because they were only medium hard. In both cases I got stuck on an obstruction while dodging barons and was slimed to death, both by single hits because the hitscanners had taken my health down. But even though these levels were not super-hard, they had a lot of brio, with monsters encountered in large numbers. E1M9 also had those annoying imps on the fenced ledges who kept sniping me, making it difficult to concentrate on killing barons. Maybe I'm a masochist, but I really enjoy being annoyed like that.
In E1M6, you were kind to allow the cyberdemons to be shotgunned through the windows. I killed one of them strictly by that method, which is rather tedious, actually. ;D The one behind the yellow-key door gave me a fun few moments. I had damaged it from outside, then went in and plasma-gunned it to death. I was surprised to find it had plenty of hitscanners to back it up, but I killed it rapidly enough to avoid being shot to death, and then cleaned out the hitscanners. A notable feature of this level is that it was very good-looking with very nice work on the ceilings. Overall, it was a superb E1-style map.
E1M7 was in a class by itself, IMO the best level in the set by far. I got killed quite a few times in this one. First, there was the Really Big Trap, which seemed to throw 8,000 monsters at me in a two-stage horror show that I found fun as hell. I got killed 3 times in that trap, mainly because I wanted 100% kills, so I tried to fight all the monsters when I could have dodged by them. That, of course, is a problem with Doom 1, which lacks area-control monsters like chaingunners and Revvies. Nonetheless, I prefer Doom 1 overall and this trap was top notch, with very fun and exciting combat.
I was killed at least 7 times trying to get the cyberdemon in the grey room with the red key, mainly because of that flesh wall you had protecting him in one of your many instant-action floor traps. Those critters dragged my BFG blasts into their hiding spot and let the cyber live long enough to blast me away again and again. I finally resorted to the invisibility sphere, which I hate, after a mutual KO between the cyb and myself. I died about 4 more times after that, but knew it was just a matter of time before I prevailed. There was one more trap with a cyb, and when I saw it open up, I thought, "Nice," because it looked cool, even though the architecture was fairly simple. That cyb was an easy kill, though. The final cyb, I must say, was an easy but tedious kill. Some of the structure blocked my BFG blasts and kept the bastard alive, and I took enough splash damage to require trips back into the level for health, but overall it was an easy kill, it just took a long time.
E1M8 was a little too easy, I thought, but those levels are hard to do.
I thought you captured the spirit of E1-style gameplay, which consists of snipers and large numbers of hitscanners walking down hallways at irregular intervals, to suddenly appear and shoot you when you thought they were all dead. I love that style of gameplay, just as I like being attacked by hitscanners and imps from several directions at once. It creates stress and a sense of panic, which is important in Doom, at least to me.
There were some things I objected to. In E1M7 there were Block Monster linedefs at the platform in the nukage pool. This prevented the spectres from chasing me up the stairs, and allowed me to calmly shotgun them to death. I would have preferred to be menaced by them. In general, I don't like block monster linedefs unless they keep a powerful monster stuck guarding an important item. Also, I object to triggering secrets by shooting at wall panels, such as computer textures and so on. This is a very obtuse way to hide secrets and IMO is a stunningly bad idea, though I should load one of the levels and see if there's any indicator on the automap. But . . . I'm not going to go shooting every wall panel in a level. Thus, I don't feel guilty for clipping to any secrets I missed. ;D
IIRC, you hid all the Soulspheres in secret areas, but there was no indication that the level contained them, so it was a surprise every time. A nice surprise, yes, but consider showing the powerup to make the player want to find it. The classic example, IMO, is the soulsphere in the original E1M3, connected to one of the most clever secret areas I've ever seen. I think your secret areas could have benefitted by being part of an adventure where we see it and go nuts trying to find the way in.
That's about it so far as complaints. The levels are good-looking, play well, and are very fun. I also agree with NightFright that your nukage area designs were very cool. As soon as I find some time I'm going to playtest your E2 and E3 maps. Looking forward to it, in fact.