I have the same thought. I'm using backblaze at the moment but am actively looking to move to either arq or tarsnap. I like that arq is in your own account and the file format is open so you can work on it yourself. Also, storing to glacier means it's dirt cheap. It's reassuring to here someone having a positive experience with it. Backblaze ha been a mixed bag for me.
Have you considered Crashplan? I've had positive experiences with it. The only downsides are that the client program uses a ton of RAM and there's no API.
