Initially, the atmosphere of the map is striking, but there is nothing really impressive about the combat or the scenery. I speak as someone who can't make very good maps either (yet). It's an interesting little relic for those who are so desperate to satisfy their M1 fetish (which apparently includes me), but I didn't get much from playing it. For better M1 scenarios available for M1A1, I recommend USS Raider and Athens Outpost. Hell, even the Two Dreary Maps challenge is kind of fun.
Playing through this pack was (literally) one big-ass blast and is done just the way I like it: Totally vanilla without any add-ons, with clever level-design and plenty of carnage. Causes you to think on your feet, manuever with grace, and strategize on the spot. No one but a team of experienced elites could have crafted map packs as strong and as consistent as these. For the whole series to be compiled like this is the perfect way to experience sadism at the hands of seasoned Marathon veterans.
My one gripe is about the level Fury: There doesn't seem to be any way to get out of that one. Maybe it was just some glitch. Honestly, I killed every single enemy, hit every switch, explored every crevice, and smacked every wall, and I would not be teleported no matter where I stood. I figured since each level is a Rebellion level anyway, I'd just quit my current game and jump to the level after that.
Beyond that, however, it's definitely a classic in my book. It had me wanting to grind my teeth at a few parts it was so difficult, but it was still hooking enough to keep me from stopping right then. Besides, every level was a learning experience: I can safely say that, fun on one hand and difficult as it was on the other, I am irrefutably a better Marathon player now than I was when I started. I highly recommend it to anyone who wants a challenge and who doesn't think that storyline is what makes a good game.