Patience. According to the Steam support site, error (10) relates to the Steam servers being busy. This is a minor inconvenience, but an inconvenience none-the-less.
And that is why I always play offline;-)
For now i only get incomplete installation error (10).
For everyone that gets this, all you have to do is try launching the game again. Then it should complete the installation. You may have to try several times before it completes. This error is usually because of too many folks trying to get the updated files at the same time.