I'm a bit late to the party, but I played this game from start to finish and I absolutely loved it.
The combination of the good ol' DOOM brutality with a Metroidvania approach to gameplay and level design equals an amazing experience all around. I could see myself having a lot of fun replaying this one in the future, looking for all the secrets I missed and trying to beat it at higher difficulties.
The Icon of Sin level in particular was amazingly done. The atmosphere is so different from the rest of the game... loved it!
Overall, amazing work, Calavera Studio!