One negative data point on waitlisting:
at the time of booking a DONE4, the system was only allowing economy even though D was widely available.
So, the AA RTW agent booked a QF domestic segment in econ but waitlisted for business.
months later, the waitlist "cleared" and the business seat was assigned.
however, when it came to travel day, QF could not check in the passenger, saying that the segment wasn't paid as business fare but rather it was booked in economy.
they also could not (or would not) take control of the ticket, so it was up to contacting AA (RTW desk was closed) to fix. 10 stressful minutes later, AA managed to fix and re-ticket.. then QF could check-in and so on.

In the future, I would not consider the waitlist option if it has the potential to cause such a mess. Of course, there was no way to know what was going on in the backend until check-in time. YMMV.