Some thoughts--especially in comparison with Dragon Age 2, which I also recently replayed.
1.) I seriously love Garrus.
2.) For that matter, I love Garrus' romance with Shepard. First, I think he's got an overactive sense of injustice that perfectly matches how I play my (paragon) Shephard; they tend to agree when something needs to be done and the only quibble becomes the method.
Second, I like that their romance dialogue specifically calls out that they respect and trust one another, and that while Garrus might feel nervous he doesn't feel uncomfortable. I've seen romances done in other video games where I felt pretty skeevy while watching the main character pursue their love interest because they pushed really hard, and seemed to be taking advantage of the other person's feelings. I don't feel that way with this relationship.
Third, they actually joke around.
Put all that together and it seems like a much healthier relationship than many of Bioware's other attempts. (Romancing Fenris in Dragon Age 2, where he nigh runs out of the room crying after sex because it made him feel too much? Yeah, made me feel like a creep.)
3.) I'm appreciating the loyalty quests far more this time around. Each quest utilizes enemies that make use of the companions unique abilities. Garrus has a overload ability that deals major damage against mechs and oh, look at this, the person we're trying to catch just happens to have a small army of mechs to hide behind!
The quests thus far also include a moment where the companion and Shepard talk about the central dilemma in the quest. It's a chance to better understand what is troubling the companion (should Mordin feel guilty over the genophage? would Garrus' revenge mission actually help anything or is it getting out of hand?) and a chance to argue your case before Shepard needs to make the actual decision at the climax of the quest. Again, this is far preferable to DA2's approach, where the player is given the premise of the quest, discovers that it's something totally different from what was initially presented (Merril's mirror is driving her away from her clan! Varric's brother is actually magic-crazy!), Hawke is forced to make a snap decision, and then the player must talk to the companion to deal with the fallout of that decision.
4.) That said, I definitely miss the banter aspect to the Dragon Age series. Companions will occasionally comment on what is going on in the mission, but they don't offer a lot of input nor will they talk to each other. That's sad to me.
5.) And, obviously, there need to be more lady aliens.
6.) Although I did like the lady specific commercials running on the asari world of Illium. "Are you using biotics to hide your wrinkles?" Teehee.