Personally I love Iron Yard and H2SO4. Those are two of my favorite maps in the new pack. Maybe they're not old-school, but I like them anyway.
It's a matter of personal taste. What I don't like about H2SO4 is the lack of tight corridors. Sometimes I want to run away from a battle when I'm low on health, but the hallways in H2SO4 are large and without any obstacles so there's nowhere to hide.
Iron Yard looks graphically nice, but it all looks the same. A little variation in the texture theme could have made it easier to navigate.
What I like about House of C'thon and The Entryway is, apart from nostalgia value, the tight corridors, close combat and non-stop action. But that's all personal taste of course.