The answer to what you say should have been your first question is that you'll have to make a final determination yourself, but Vail is a beta product at this time, with known issues that include the possibility of data loss. It's not supported for use in
a production environment, so you should assume that any computer you connect to Vail is unprotected by Vail, and that any data you place on your Vail server will vanish overnight some night.
For the first question: No, you can't have both versions of the connector installed. The Vail connector will refuse to install if the V1 connector is in place, and while the V1 connector will install with the Vail connector already installed, Microsoft has
warned that doing so will leave the client computer in an unknown state, in which it may fail to back up to either server, and it may be impossible to remove either connector without flattening the client. Having both connectors installed is not, per Microsoft,
going to be a supported scenario.
I'm not on the WHS team, I just post a lot. :)