I just recently wrote a very detailed review about the WiFi on the A350's including speed tests on two different flights.
https://www.flyertalk.com/forum/trip...-all-wifi.html
The WiFi is not free for anyone even PPS card holders in Business Class... Everyone must pay or log in using a roaming partner (either iPass or Boingo).
Currently, a 3-hour pass costs US$16.95 and a 24-hour pass costs US$21.95.
If you're connecting to another SQ A350, B777 or a Scoot 787 flight then you can continue to use the 24-hour pass whilst onboard (but note the 24 hours is valid from when you first activate the pack and can't be paused).