My recent trip had the chance of using the diners club international lounges in Singapore (SIN) and Berlin (TXL). The SIN Ambassador Transit Lounge (terminal 2) was very nice, with shower, hot Asian food and free WiFi. The TXL lounge was okay, and the WiFi was not free.

The US-issued Diners Club card did not work for SATS Premier Club Lounge (terminal 2) in Singapore when I used it last year.

Just thought that it might be useful for other travellers. The lounge access has not been very consistent.