I especially didn't like Hawke as Reaver, simply for roleplaying reasons. I felt sorry for the poor bastard who thrived off of "pain" the way Hawke did. lol.
Hawke has a lot of tragedy in his/her life. Reaver kind of puts a whole new spin on it, storywise.
Not because it's dark or evil per se.. it's just sort of tragic to give in to grief like that. I wanted Hawke to be more optimistic, psychologically speaking.
You know, I was always so focused on the Templar aspect of Hawke that I never put much thought into the Reaver aspect... I always saw it as a source of power, nothing more. Something he earned when he killed his first mature dragon in the Bone Pit. I never thought to draw parallels between the spec and his storyline, but I have to admit, this does make sense...
edit: I think the issue is that I didn't put much stock in Hawke's emotional pain. Even when his mother died, he seemed sad (depending on dialogue options) but that was it... and there was really no time to even consider what had just happened since we were immediately setting off for another quest. No funeral, no time spent wallowing around in his house... so yeah... Hawke seemed pretty emotionally detached from the people around him from what I saw. But again, that might depend on dialogue choices as well as personal interpretation.