@TN You should give it a try, it's great fun.
@Mystery The character interaction is a definite big thing for me because I love how lifelike the characters are and how much I grow to like them as I continue to play. For number two, I was desperate to ensure that, well, you know, the end played out the appropriate way.
For characters, I like Joker because he's hilarious, Liara (my primary romance partner for my FemShep), Kelly (whom I love) and Jack. I've honestly loved all the squad members I received throughout the game because they each added something to the table. I'd say my least favorite was Kaidan from number one, but that wasn't due to his persona.