I am very interested in what you think of Valhalla. I only have the reverbs that have come with Sonar. I have been using Breverb since receiving it, but it always sounds a little harsh to me, for a lack of a better description. Basically, as Clint mentions, on vocals especially, I am just not satisfied with Breverb, unless I turn the wet down until reverb is barely noticeable.
Every forum that I frequent, Valhalla always gets rave reviews.