Fix Office bugs for existing features in a timely manner. Offer a bug bounty program?
Offer a bug bounty program (could be non-monetary e.g. subscription extension, free licenses etc), so users have the incentive to submit reproducible, well documented bugs as soon as discovered. Repro step-by-step instructions with file samples could save the developers quite a lot of time in diagnosing and fixing bugs.
Kenneth Barber commented
I think that this is a good idea as long as the term "bug" is clearly defined. Sometimes, people call inconveniences or the lack of a feature as "bugs".
Take the YASARA crew for example. They are much poorer than Microsoft but are much more generous in their rewards for bugs and suggestions.
I have heard that MS doesn’t typically fix “all” bugs in Excel, because changing existing behavior may actually break the (faulty) solutions of other customers out there (!). But they would definitely consider all bugs and are especially likely to fix regressions that only appear in the current version of Excel (Office)
There are several reporting channels e.g via MVPs, Office blogs etc, but I don't think bugs & hot fixes get the priority they deserve.
Bill Bekenn commented
I would use such a reporting system, even if there were no bounty. There are some quite serious bugs that have been there for years, and I just learn to work round them because there is no easy to use reporting channel.