Some of the romances took a nosedive. The Tali one is great, except I wanted an option for my Shepard to ask about her early on. You don't get her 'til later, and at that point it's like she didn't exist to my Shepard, who was definitely already in love with her, based on how ME1 and 2 went. So like, that bugged me.
The way they handled the love triangles was bull**** if you romanced an ME2 person. You get confronted once by another LI, like Liara, and asked if you want to be with them. You can say yes, then you are. But when you get to talk to the ME2 romance again, they ask you what you want. If you say yes to them, the other person you said yes to ends without a conversation. Happened to me with Liara and Miranda, I was pissed. I expected to have a catfight, but no. I said yes to Liara, then yes to Miranda, and I was stuck with Miranda and Liara had one random dialogue spout to mention it when I went to talk to her. I was annoyed that the game doesn't let you know. I realize they're making it realistic in a sense, but Liara shouldn't just automatically figure it out. That was pretty stupid.