I love the convenience of what ManageWP offers but I'm also concerned about the security more than the price. If their encryption key gets compromised then the backups of all of their customers are compromised. And those backups all contain the database login information. It just seems like it's asking for trouble.

I would only consider using a service like this if they provided a full trust-no-one (TNO) model where I supply my own encryption key that they never see and my data gets pre-encrypted before leaving my server. Other options might be to allow specifying my own Amazon S3 account to store backups as long as the data never goes through their servers on the way.

The ideal would be software I can run on one of my own servers and fully control and secure. I'd be happy to pay for that.