Completely overhauling a team that got promotion seems to be working for Sunderland as it did for Forest before them, but as I mentioned previously both needed to do so having only been promoted via the play offs, and so had a weaker starting position than those promoted automatically.
It doesn't always work though. Ipswich previously had a similar team ethic that we seem to have this season and spent big in the PL, but having then been relegated and despite having a very strong squad on paper, are struggling to find that togetherness they previously had.