I ride an Arbor, as does my husband. I would say they are very high quality boards overall. My husband has the Roundhouse and loves it - he finds it very responsive in the trees, it holds a great edge, is super fast, and is solid in powder. He rides it pretty hard and has had no issues at all.
I'm not sure if others would agree, but I find that Arbors are stiffer than similar boards from other manufacturers. I bought the Eden (Arbor's women's progression board) expecting it to be a good board to learn on, but found it too stiff to turn easily, so it has been retired until I can be a more aggressive rider. The Roundhouse, and a lot of their all-mountain or freeride boards are extremely stiff as well. I don't know much about Arbor's park boards.
Beyond that, Arbors are just beautiful pieces of art. Random strangers comment on my husband's Roundhouse all the time. We board at Mt. Hood and people who ride Arbors notice other Arbors on the mountain - like there's some kind of brand kinship or something. I've had many a conversation with other Arbor riders as we've strapped in at the top of a run, talking about our boards and how much we like them. It's kind of weird, actually.
So yeah, Arbors are probably not for everyone, but are certainly quality and worth consideration.