I hadn't heard them, so having read the messages above I just had to go to their website and have a listen to the soundbites they provide.
On the basis of what I heard there, I have to admit that they did not light my wick. No bad, but I wouldn't fight for a ticket to one of their concerts. Tight harmonies, yes, but they are not unique in that. Nothing special enough for me and my tastes.
Having said that, perhaps they are more engaging as a live act; this is true of many performers. In any case, good luck to them, but I won't be buying any of their CDs. No hard feelings, I expect they wouldn't buy one of mine either.