i liked a LOT the LemCo style, both in buildings and interior graphics, and the fact they are inspired to his leader by Jules Verne (iirc, i've read that he was fond in 20000 leagues under the sea), and the chance to explore those ruins to find loot is a satisfactory experience for my playstyle: to be honest, i've liked a lot more the DLC experience than the original one, not because the latter is worse, but because the DLC inspire me more, with his aura of mystery that gives the idea you can find a real treasure just behind the next corner, or death... and you will find both, many times XD
I loved the ski jet ideas, and even the fact that the sunless sea do not have too much human presence around, except where it's concentrated, the only drawback i've found so far are the fact that jets are not exactly that useful as i hoped for, it's way too hard to refit them with good components are they're too hard to find, and combat with them is a royal pain, as i got killed a pair of times because enemies hits my jet with a sniper attack, instantly sunking the jet with me on top.
Anyway, the whole place is great, the quests are okay and sometimes a surprise (like having pickpocket this time proved to be very nice)