I looked at the Salk SongTowers as well-never demoed them, so no call on that. However, I think the reason you don't hear much about the center is that I do not believe, to my knowledge, that it has been available for a very long time. That, coupled with the small number of people that have actually taken the plunge on these, from what I can tell, well respected by those who know about them, speakers means there is not much news about them.
It would be great to see Audioholics do a review on a Salk setup though, I think it would help several people out since more and more seem to be asking about these speakers.