Viewed as a sort of "Mission Pack 3", continuing on from where Scourge and DoE put things but with a modern perspective, Sacrilege is a really good set of episodes, with its own personality (and "Doom" style handdrawn map images to start each one off to let you know where you are).
Monster variation from progs_dump is used with the right amount of self-control... although the nailgun grunts (and lieutenants/supernailgun grunts) significantly increase the difficulty level of the game.
I started out on Normal - having just completed Scourge again on Hard - and this felt harder than Scourge-on-Hard, enough that after 2 and a half levels I had to go back an restart on Easy. Easy, by contrast, feels somewhere around Scourge on Normal...
As Mazu says, part of this is that some of the enemies make things a bit quicksavey - there's a few situations where you either get the enemy in time or you lose half your health.
That said, it's always nice to see gremlins in a map - although I do think the little guys need something to make them do their interesting behaviours more often (maybe QuakeC just isn't up to it...).
I had a lot of fun with this in general, and usually if I got stuck in a level it was because I hadn't noticed a lightpanel or a climbable section because I didn't look up enough.
There's a sudden difficulty swing at the very last few levels of the game - S3M5 and Send are both much harder than the rest on Easy - and basically the only bit I had to godmode through was the final battle. (The
starting battle in SEnd I needed a lot of goes at too, but I could at least see how to do it
.)
Anyway, charming, has gremlins, and almost entirely great on Easy, so 4/5.