I am using the PHY KM30 SAG in an open baffle. I am ecstatic with the results. Unlike Mbhcid, I wouldn't describe them as warm and lush in my system. But then again, he is using them with a 2A3 & 300B. I am driving them with a Berning ZH270 which would explain a lot of the differences we might be hearing.
However, I would agree with Mike that they play BIG with fabulous imaging, great tonality and a realism that is spooky at times.
I am using a Velodyne DD12 to supplement the PHY's below 40HZ, but when I turn my sub off, I really don't lose that much. But I do think my system sounds better with the sub on.
I won't be going back to boxes anytime soon. I am sold on the amazing "openness" of an open-baffle design. Quite frankly, I am surprised at how few have tried OB's. I am certain that many would be shocked at the OB sound compared to boxes.