I'm for darker nights. Would be even cooler if the night darkness was reflected by the moon phase. Where a no moon would be near pitch black!

Even different NPC's may come out at this time that may be more sinister and deadly than your normal night time mobs. Wights are always a fright when they come out at night! (oh crap did I just rhyme? lol)

but if they make things darker we need items like lanterns, candles, torches and mystical orbs to light our way!

I would love to go splunking in caves that I couldn't see much further than 10ft in front of me. I wouldn't want them to be ALL caves because it would be annoying. But make a few caves like this, and make them worth exploring to find treasure or good loot to be worth the effort to buy these lanterns and torches