Is it safe?
I don't mean to be difficult, but safe from what?
Is the data encrypted?
Yes, it is encrypted in transit. No, it is not encrypted on our servers.
More detail here:
http://forums.omnigroup.com/showpost...50&postcount=2
Is it free? Yes.
As an Omni employee, I suspect my opinions will not be as valuable as other forum members, but will note that I sync my own OmniFocus database via Omni Sync Server.