Just completed it. It definitely needs updating, but that's not going to happen as the author does not have the files anymore.
But despite that, it was a joy to play and watch Alex Diener play at the same time (Check him out on youtube).
Major issues:
There's a skill called Tricks and Traps, it does nothing.
If you use the elemental orb things you get near the end of the game, on the places that you use them in grimrock 2, then they disappear and are impossible to get back, reload a save.
There are many new spider models and they wig me the hell out. So if you have arachnophobia, give this mod a miss.
Minor issues:
The English is really poor. It can be funny to read, but sometimes you need to use your brain and work out what things say. For me that was no issue, most of the time. But I can understand it might be difficult for dyslexic people, or people for whom English is not their first language.
Some puzzles you really have to be able to read minds to work out how to do. (Alex Diener's videos help a lot again.)

Unknown if they are issues:
There are many staircases that are simply inaccessible. As well as chests that you cannot reach. (Top of the wizards tower has a room with two chests,but you get teleported out every time you go into that room. No chests for you.)
Sometimes quest items don't spawn on you, but rather quite a bit away from you.

Ultimately, I recommend this mod to all who want more legend of Grimrock. the base game is not long enough, this is several times the length of the base game. I'd put this on a shelf next to Adrageron's mods. (Lost City, Guardians, Final Adventure), the puzzles were challenging, the bosses were really tough, some of the bosses even require out of the box thinking, you can't just go in there and smack them.

Finally, I've spoken to the dev in youtube comments, he's super chill and is currently making another game: Underkeep. His English has by far improved, so go wishlist that!

Go play it, stop reading my comment, go enjoy it for yourself! <3
P.S: Despite the mods recommendation, Alex Diener completed it on Normal. So if you don't want to play on Easy, you don't have to.... I played it on easy, it was bloody hard, but hey, maybe you're a masochist. XD