Tyrone x Tasha: I think Tyrone's more laid back nature will bring out Tasha's more sensible side, while Tasha's bold side will help Tyrone to become more strong willed.
Uniqua x Austin: Uniqua's social and confident persona seems to bring out the best in Austin, as does Austin's quiet and patient personality for Uniqua.
As for Pablo, well:
Pablo: Wow, my friends fell in love. This is so wonderful. I can't believe it…
Tyrone: Pablo…
Pablo: … how did this happen? I haven't a clue, but stay calm…
Austin: Pablo…
Pablo: … we've all been friends and now my friends are in love…
Tasha: PABLO!
Pablo: Yeah?
Uniqua: We're just friends.
Pablo: I see. (To self) Keep telling yourself that.