I agree -- Revivals is low-key, not high energy, and really good for relaxing a bit before heading into the rush of London. Particularly good if your flight arrives hours before you can check into the hotel. My guesstimate based on recent observations is that only 10% of eligible passengers actually use Revivals -- the others are either transferring at LHR (and hence use the Club House) or are going straight home from the airport and don't need an arrival lounge.