Treek can be either a Tank or a HealerTreek can be either a Tank or a Healer. As a healer she (yes, she!) is at least on par with other healing companions, but she really shines as a tank compared to all other tank comps. She uses taunts intelligently and has better threat generation in general.
As of Patch 4. As a healer she (yes, she!) is at least on par with other healing companions0, but she really shines as a tankTreek offers absolutely nothing compared to all other tank compscompanions. She uses taunts intelligently All companions can now tank, heal, or DPS and has better threat generation in generalare equally proficient at them (apart from minor differences between melee and ranged companions).
She has affection conversations, but no associated quests. The conversations differ based on your faction. She does not unlock anything for crew skills, sadly, but does have a +1 Crit bonus, but does have a +1 Crit bonus.
TL;DR: She is not worth the money at all.