So much time was spent making Sven a foil for Marten... a skinny indie rock nerd, a guitar-player and songwriter, a connection to Dora, even a similar sense of humour. Except, of course, he was an amoral, womanising asshole version of Marten. Yes, one with a soul who can be nice and charming and has feelings, but he was always put up as sort of an Anti-Marten. He never really formed any attachment with the rest of the gang, and aside from occasionally hanging out with his siter and bumping uglies with Faye, didn't interact with the others except for a few rare occasions.
Angus has been set up from day one to NOT be like Marten. He's the first guy who seems geniunely unafraid of Faye, can actually hold his own in witty banter, but has none of the music-nerd cred that was basically what started Marten and Faye's friendship. Instead of following her around with doe-eyes, or doing everything he can think of to get into her pants, he's been perfectly willing since day one to slap her with a sassy retort and walk away, even if he does come back for another round soon after. He's formed genuine friendships with everyone by being persistent, nice, and just weird enough to fit into their group.
When Faye couldn't form a relationship with Marten, she clearly wasn't over him. She said as much more than once. And when she had a weak moment around Sven, she slept with him because he was the closest she could get to the guy she wanted and couldn't have. And then, when Sven proved he was definitely *not* as decent a guy as Marten, she walked away. And she kept suffering because she still wasn't over Marten, not really. But now? After a date and a goodnight kiss from Angus, she finds that she finally is.
In short:
Angus McPhee, the line of your ancestors stretches back to Valhalla. Ride, my son. Ride 'til you find them.