When I first saw advertisements for the CBO, I didn't think it would be that great. Cheese, bacon, and onion on a burger/chicken sandwich. Big deal. It's been done only about a billion times before. I opted for the crispy chicken CBO and it's the best chicken sandwich I've ever gotten at McDonalds. Granted McDonald's isn't my go-to fast food restaurant for chicken, this surprised me. The bun is -- apparently -- whole grain and isn't normally used at McDonalds. It also has a hint of sweetness to it, which I approve of against the saltiness of the bacon. The bacon isn't that great (it seems microwaved, to be honest), but the onions, and especially the sauce, make this a sandwich well worth ordering.
I haven't had the angus CBO, but I think it would be fine. Not quite as good as the crispy chicken (the sauce just goes really well with it), but no doubt tasty.
+: The bread. The sauce. The sandwich as a whole.
-: On its own, the bacon is underwhelming. Small. Somewhat expensive for what you get.