I'll give it credit where it's due: the map is huge, beautiful to look at, rendered in hi-def, and has lots of room for notes so you can make it your own. Unfortunately, I don't ever see myself using it.
The map is big, but its design is bad. It's full of dead-end branches and single-entrance rooms. This might not seem like a big deal if you've never run a big dungeon before, but "we enter the room, we deal with the stuff in the room, we return to the corridor and go to the next room down" can reduce a dungeon delve to monotony real fast. And in a megadungeon, it's imperative that exploring the dungeon doesn't get old. The way around this is simple: make sure the PCs always have at least 2 ways forward. Connect dead ends into loops, and make sure rooms connect to each other and to other corridors, rather than one corridor connecting all the rooms like houses on a street. This map fails to do this, and as such would be pretty monotonous to explore - I want to offer my PCs better.
The other gripe isn't a deal if you have access to a printer and don't mind running from a printed copy, but I don't and do, respectively. The PDF is not form-fillable.
I really recommend generating a map and then tweaking it instead of grabbing this. It's much easier to tweak a simplistic map like the ones on Donjon into a good design than it is to edit something graphically detailed like this one. Otherwise, just roll and sketch out your own. There's a lot of methods for generating a dungeon quickly, and lots of easy (free) software like Dungeonographer and DungeonDraft to help you get it digitized.
Pretty as it is, I just can't recommend this.