I've used it for god knows how many times now and I think it's a true godsend for those arriving on 251 and 255. The shower rooms are huge and there's plenty of them, so there's never a queue (unlike the CX one in HKG). Breakfast is quite decent with your usual variety of hot and cold items.

Just to clarify, the access rules are either class of service (F/J) or tier status (DM/GO). Remember to ask for an invitation at HKG check-in.