Priority boarding: Certainly at YPPH/PER and YMML/MEL I don't feel like it is done well, its a mess of people standing around and often having to fight through a crowd of people.
In-flight Wi-Fi: Maybe my recent flights have just been unlucky but I've had three different airframes recently, including one that had the fresh fit-out, that still lacked wi-fi. While not having it is a good excuse to try and switch off from work for a few hours, when travelling for business it is helpful to have the access and its one of the few valuable platinum benefits remaining...
Food: Yeah, both lounge and onboard the offering is uninspired and bland. I may be in the minority here but the previous ham and cheesy toasty on board in the plastic bag was at least edible, the new one in the cardboard box is dry and miserable!
Lounges: In general I've found lounges in Perth, Brisbane and Melbourne recently bursting at the seams on multiple trips making it near on impossible to find anywhere to sit, with some of the lounges now also feeling quite tired.
New fit-out on board: The new layout feels like its reduced the Yx space and I feel for whoever sits in 3B or 3E in the new design as that extra leg room gets even more limited with the J seat replacement taking up a lot of the space for their feet/legs (or bag). The shower curtain also looks stupid and I empathise with the poor crew who are left trying to do to right thing defending the business cabin area, but even this is inconsistently enforced as someone who often sits in row 3 and watching people meander past while some of us do the right thing and head to the back.
Platinum upgrades (x4): Much like you Matt G, I struggle to make use of these flying on busy routes, even when there's one seat left its often not been released to be used for a platinum upgrade...
I know this has been a topic of conversation elsewhere but as someone who's a VA Plat flying out of Perth for work interstate I've felt like a lot of the recent changes to the loyalty program and a very inconsistent experience across both lounges and on-board have left me wondering why I bother in someways - the platinum experience certainly feels like its devalued greatly (ignoring earn rates etc.)