They look quite neat I think. I am not a fan of the mufflers being on show (would prefer black myself so they hide), and dont like how he has cut out part of the rear metal grille (is that what its called?). Looks like the twin tips would not fit in the standard space between the bumper and the metal grill.
Also, on some cars the space for the tips is round/oval, and twin tips in the one hole look a bit weird, like the previous gen liberty STIs.
One of the guys in perth had twin central tips, looked quite neat, and certainly very unique.
Its just a personal preference in looks.
Cheers