I use priority inbox with custom queries too, so that's the missing killer feature for me. Right now I just use standard priority inbox with the four slots (starred, important+unread, unread, everything else) but multiple inbox with five sounds pretty good now that I see these queries.

I'm pretty hungry to switch from Spark and their intermediate servers, and I bet I'm not the only one. At work I use full GSuite integration, so am pretty much stuck with Wavebox or another Electron aggregator. But for personal use this hits exactly the right spot for me.