Hey Ivan, I am in the process of upgrading to beta 2. Did the extension methods move to a different namespace?
I am having the same issues with other functionality I have built as well (such as Albums, for example).
It appears that App.WorkWith().Albums() returns an AlbumSingularFacade rather than an AlbumPluralFacade which does have a Where(Exrpression<Func> what) method. Is this intentional?