I only use the app version Brendan - although I do have several hardback editions. The app solves anagrams as well as the dictionary mode. It's excellent.
... The app version is missing some minor sections - it doesn't have the section on first names that some hardback editions have, so it's occasionally useful to have a hardback edition too.
Hi again Smartie, I've just bought it and realised I've got enough left over for the Chambers thesaurus. The first thing I did was enter 'Rayne' and it immediately came back with 'Obsolete or Spenserian spelling of reign - excellent!