Played multiple times on a full server and thought pretty well of it. I compare this to cp_steel since players get lost and confused with non-linear objectives. They did catch on after a while of back-capping D right away, which lead to a more enjoyable experience with more people learning the map (and properly defending).
I remember disliking the map at times after B, where it felt more maze-like and objectives were farther away from RED spawn. Compared to Steel where defenders have a reliable corner to approach a defending point, this was most noticeable on C located at a different wing of the facility. C felt weird to defend as an Engineer with attackers able to flank a Sentry from both angles.
Additionally, I saw a lot of empty space used for boring travel rather than combat, a problem I didn't see with Steel. This was most apparent on the A-C flank or the B-C side route, and I think this problem stems from the objectives being spread far apart.
I congratulate the design and originality put into Hadal.
I have not had this much fun on a tf2 map in a long time, the map is beautiful and runs well on my ultrabook with integrated graphics.
The map has meny routes to the different areas and gives ample opportunity for both teams to flank each other. I played Pyro for the most part and found that the detonator suits the map perfectly. from the short time I played I didn't feel like it was impossible to push/hold and that the map avoids problems other similar maps tend to have. I strongly recommend this map!