If you hold a Lufthansa first class ticket, the separate terminal is worth structuring your connection around.
Access is restricted to Lufthansa First Class ticket holders and HON Circle members — you cannot buy your way in with status alone on a business class fare. The terminal sits apart from the main FRA complex, with its own security and immigration processing.
A Porsche (or Mercedes for larger groups) collects you from your arriving gate and drives you directly to the terminal entrance. Inside, white-tablecloth dining with personal service replaces the buffet model — I had a full three-course lunch with wine pairings before a 2pm departure.
The spa offers massages and showers, and the seating areas are arranged for privacy rather than capacity. During peak morning banks it can fill, but never to the point of feeling crowded. When it is time to board, another private car drives you directly to the aircraft stairs.
If you are connecting through Frankfurt on a First Class ticket, build at least two hours to use the terminal properly. It is the single best ground experience in European aviation and justifies routing through FRA over Munich or Zurich for First Class passengers.