I've been running Maze of the Blue Medusa using 5e off and on for the last few months. The group has consisted of:
- Kenku Raven Queen Tomelock
- Tiefling Kensai
- Half-Orc Samurai
- Half-Elf Whisper Bard
- Yuan-ti Pureblood Immortal Mystic
They are rarely all present at once and much of the game has been with 2-3 PCs present at any given time. We started at lvl 5 and are currently lvl 9. I own the book.
I converted monsters on the fly either by choosing their nearest equivalent in the MM or by matching them thematically to a certain monster. (Ex: I converted the Orchidmen found in the Gardens as half-strength Mind Flayers). Most of the time though I used the stats in MotBM as is making only minor adjustments before an encounter. My prep time was usually 15 min or so for a 4 hour session.
The biggest thing about the dungeon for me was the nature of the portal that leads to it. Depending on how you interpret the portal, the party might not have a reliable way of leaving and re-entering. The book itself seems to assume that the party will enter and have trouble leaving (and depending on the encounter in the first room, they might not have a choice if they can leave), but it never states outright which way to interpret the portal. I devised a background plot to explain how the party could enter and leave week to week. The party also has numerous ways to reach the various themed regions of the dungeon and they layout of the dungeon feels very maze-like and sprawling.
I had a fun time running, but I do think that 5e characters make some of the challenges of the dungeon trivial. There are many rooms where the floor has some magical effect that low-level teleports and short-range flight made superfluous. I think while the Maze is designed as system agnostic, it would work best with a version of D&D where the characters have less innate magical resources. If I ran it again I would definitely use a retroclone.
I ran it using the physical book and I think using a PDF would have been more difficult. Each region's layout is a small map with brief descriptions followed by longer room entries with a full dungeon map in the front of the book and a seperate section for npcs. If you're good with bookmarking your PDFs it might not be a problem, but I found myself slipping through the book a lot during play and would have had a tough time with a PDF.