As a Brit with an Aussie partner, I find this whole sordid affair pretty depressing. I think it's a poor decision on the part of Australia and is against her best interests and ignores her fairly important and critical security needs.
Here's my 2c worth...
I suspect that the RAN isn't thrilled with this, as it compromises their autonomy to conduct operations, and even ensure availability of their own vessels. It also fails to address fairly obvious security priorities (see below). I suspect they'll be some very angry words in private between politicians and navy personnel who feel they've been compromised by politicians who either desperately want to grandstand, or caved into US pressure, or - more likely - a combination of both. Scomo has consistently shown his vulnerability to ego massaging and flattery.
The main problem is that American (in particular) and UK (to a lesser degree) SSNs are designed for use out in the big blue, with lots of depth and nothing in the way. Australia's main maritime security headaches are almost all along her northern coast, which couldn't be less suited to SSNs. Scomo probably ins't terribly familiar with anything outside the eastern suburbs and northern beaches of Sydney, but if he ever cares to take note, he might notice that pretty much the entirety of the northern coast is extremely shallow, very VERY tidal, and littered with estuaries, islands, reefs, shoals and shifting mud and sand banks. It's *much* better suited to a small, agile diesel-electric sub. The German/Italian Type 212 can operate in 17m of water and would be infinitely more appropriate to Australian needs, which really boil down to stopping a potential landing or blockading force.
The other thing is that for all Scomo wants to be America's jack russell, he's more like the cop at China's shopping mall. Australia is the biggest buyer *by far* of Australian exports.... Iron ore is Australia's #1 export, and 70% of it goes to China. In pretty much every major commodity Australia sells, China is invariably the #1 buyer, and in several major sectors is the overall majority buyer, with the rest of the planet making up the remainder. Many sectors like agricultural development and real-estate also rely heavily on Chinese investment. Gambling the entire economy on how amicable towards China some random American foreign policy hawks are going to be doesn't seem like a genius move.
Finally, the existing Collins submarines, though not the world's best, are the only submarine solution Australia currently has, and given this AUKUS thing doesn't actually provide submarines, just some vague commitments to share certain tech, Australia seems incredibly unlikely to be able to get a replacement in the water in time. To be blunt, the chances of Australia being able to domestically produce an SSN is low to none. There will be a decade of mill of umm-ign and ahhh-ing, harrumphing and finally some bodged last minute deal to either go back to diesel-electric, or, worse buy some used or poorly adapted off the peg SSNs that massively compromise Australia's legitimate maritime interests while pissing off France (as in New Caledonia) and New Zealand - Australia's closest allies in the region.
