I had no prior interest in AXS, but recently got a clearance gravel bike that came with with Rival Etap. My experience so far is that it works reliably, even when things get a bit wet and muddy, but I can’t see any real performance advantage compared to a properly set up cable system.
The price is the biggest downside (I think the retail group set costs more than the total price of the entire bike I bought on sale).
I’ve no technical complaints about AXS, but I don’t think I would go out of my way to spec it if I was choosing the bits