My favorite part from Nehrim has to be traversing the underground ruins. Dwarves, ancient ruins, and subterranean worlds are all some of my favorite fantasy themes, so that part was one of the most memorable ones for me. Blackreach in Skyrim was a pleasant surprise for me, so I'd really like to see what you can do with the new engine.
I don't think you will have to worry. If you have seen the early gameplay video you can already see that there are some underground places, see http://y2u.be/ZHu4xR6d3nA 00:55, 01:13, 01:30, 2:39 (!!!), 2:49, 4:28, 4:46 .. and that's just the FIRST video. In Nehrim there are 50+ underground areas/dungeons so.. I doubt they will somehow fail to add a good amount of this goodness into Enderal. What I've seen so far is just amazing, no need to fear! 
Well I don't mean just caves and stuff, I mean like the Dwarven ruins in Nehrim, or Blackreach in Skyrim.
Well, considering that Enderal is another worldspace/realm than Nehrim, I don't know if there are any dwarves (Starpeople) there. We'll probably just have to wait and see, but I'm sure we'll see something in the likes of it, the starpeople were really cool and there were a lot of awesome designs made. The quests that involve the starpeople are also quite lengthy, and as you know, there were several different dwarven areas, like the abandoned docks in northwestern Nehrim and the place near the Apple Horn Court with the sub?... I don't think we've seen the last of the starpeople yet. Question is if they ever managed to fly somewhere else though; but given they found their way into the Tower Defense-realm there's a fat chance they could've found Enderal or any other places too! 
I hope the Star People return form their homeworld where they've found their lost secret of Beards.
The Starpeople were more unique then your stereotypical fantasy dwarf.
Do you recall ever seeing any female Star People? That's probably why they are so anxious to return home! 
Not that I can remember
Perhaps there will be something like Zerobilon in Enderal and if we're lucky we can travel to a place where there are star women! 




