Just finished the 3rd map and it's still a blast to play! I can't think of anything too different without sounding like a broken record, it's still exciting and the maps are alive and feel like a tech base.
It may be because I'm garbage at this game but the hall full of hit scanners really felt like a huge jump in difficulty, maybe put map 3 a little later in the full WAD or tone it down a bit. Just an idea though.
Can't wait to see the next challenge in map 4!