All of the locations (ESPECIALLY in the Commander Lillith DLC) are absolutely amazing. You're constantly getting new guns, or you can farm bosses you've killed for their assigned legendary (which is a pretty ingenious system). Staying spoiler free, everything that happens in this bossfight is just perfection. One of my favorite boss fights ever is Control Core Angel. Handsome Jack's development as a character was very cool to watch be played out. I didn't play BL1 first so I was actually really surprised by the Angel plot twist.
You can constantly find out new information about the characters. All of the characters are really charming and fleshed out, I was worried that claptrap would end up being a 'jar-jar' but he ended up being a really funny character. The characters, the story, the loot progression, locations, weapons, everything here is perfect.