Thanks to Maria Doyle, Application and Training Specialist at Peter MacCallum Cancer Centre!
Thanks a lot for this feedback! It's great to know other people are finding the built-in annotations useful (as am I) :)
Btw in case this is useful to you to know, I'm finding that the output of featureCounts with those built-in Entrez/RefSeq IDs is working well with the Galaxy tools annotateMyIDs (e.g. for adding Gene Symbols) and EGSEA (for gene set testing/pathway analysis/heatmaps).