I've just returned from a Star Alliance RTW itinerary that included SQ for several segments. Rules for RTW tickets allow changes in flight dates with no penalty (but not changes in itinerary without significant difficulties).

SQ was a ..... about every change in date that occurred, and claimed that the flight couldn't be seen in their system and/or required a "ticket number" that, with a E-Ticket, of course didn't exist.

There are significant problems IMHO with the computer connections between Star Alliance carriers. Changes with UA and LH were no problem, but SQ has enormous problems with accessing these records (telephone calls to UA reservations were required in SIN, BKK, and PVG) even when SQ could see the reservation in their record.

I am mostly unimpressed with SQ, despite glowing reports by others about this airline. Staff seem mechanical and phony, and when anything not "in the book" occurs they freeze up like deer in the headlights.