From the moment this caught my eye I was absolutely enamored with the approach. Maybe it's because of the notable similarities in color palette with the Bullhearted Creative Co. Call me biased. It does go beyond that though.
O2's identity is lead by a simple typographic lockup paired with a whimsical, slightly edgy rabbit illustration. The boldly simple O2 is easily identifiable from far away especially with the high contrast of black over top of fluorescent green-yellow.
One shortcoming is the difference in weight between the "O" and the "2" which is a common problem when setting type at two different X-heights. A work around here would be to thicken up the "2" to be more comparable to the "O" thereby creating more adhesion between the two.
What would be a minimalist type of brand identity is completely disrupted by the whimsical rabbit mark that finds itself used sparingly, but powerfully.