Alpha Implementation indicates a feature where developer confidence in its functionality has not yet been firmly established. This typically includes brand new features for which adequate unit tests have not been completed, and/or features whose scope is broad enough that its not clear what additional unit tests might be needed.
Alpha implementation is not meant to discourage the usage of a feature, it is only meant to indicate that some difficulties in getting full functionality from the feature may occur, and to encourage the reporting of these difficulties either via the mailing list or through submitting a ticket.