I think you're getting a little off the subject. The question of just how medieval and/or renaissance music (or for that matter 18th and 19th cent music) sounded would make a highly interesting thread on it's own.

Artbrooks asked for opinions as to whether the group is well-known, and if it's worthwhile making some effort to hear them. I would say if you have the opportunity then try to catch them. On the merits of the one CD I have I think their arrangements are imaginative and impressive and the quality of their singing superb.