For me; picking up the PSL in a reasonable timeframe & just the flexibility there.

As for on board; nothing much but when food options are limited it would be nice to asked first.
Would be nice to reserve hand luggage space as I saw them do recently for another passenger who was boarding just before boarding finished.
If BOB gets introduced; a spending limit or something as they did for Ultimate.

After the most recent “enhancement”; not having to pay for bulkhead.