It's about what I'd expect from a Steam/Raptr Clone, but the ability to buy zen in the overlay looks nice. No money to test it with, though.
The biggest hurdle I think it will face is the fact that the Arc overlay overrides others, like TS3Overlay. Also, the developers need to make sure that the RAM footprint of Arc is as small as possible.
As a final thought, DO NOT make Arc a requirement. There will be people who don't use this type of program, don't force them.