The documentation is fair enough within Xcode to figure most things out by yourself, but there are plenty of resources online when you feel like needing some help.
I like the updates they are doing to Swift Data for the next round of OS updates, these should make things even easier and more straight forward to build certain Apps.
But yes, there are things to watch out for, make sure you learn the foundations well (e.g. @Observable, @State, modifiers), or you may find some unexpected things happening with no clear explanation.
Also keep in mind that not everything available in UIKit is available in SwiftUI, but there is plenty to cover lots of use cases nowadays.
You can also do some SwiftUI stuff outside Macs, there was this effort to bring SwiftUI to terminal, as in Linux. Ashen was the name of the project, but I believe that it hasn't received many updates lately. There are also recent efforts for Gnome if I remember well. And there are also some other general Swift updates that are very interesting, like Swift for micro-controllers or whatever they are calling it, and being able to create static Linux binaries (and do so directly from your very own Mac) without any dependencies that can run on any distro (or so they said IIRC), and built with musl for good measure apparently... again, or so they mentioned in one of the WWDC videos.
So... not so bad, but with all that said, I would like to add that, I really would prefer not to have any AI forced into any of my devices with the next update.
From what I understand this hasn't stopped. If you are a full-time dev and you are willing to price your app well, go for it. It's a nice big market, and people do pay for apps. It would be a pity to stay away from that market if you can afford to keep updating bits and pieces of your code every now and then.
The other annoying this (which I don't think it's been resolved/avoided) is that back in the day you could only develop code on a Mac, which you can always buy a second-hand one, and a couple of iPhones to full-around with (although Xcode can simulate all devices so you can test UIs, etc.)
You probably don’t want to target lower than iOS 16 if using SwiftUI since a lot of nice APIs aren’t available on lower versions.
We used Catalyst in work for bringing our iOS app to macOS and it’s been good enough.
It may be Stockholm syndrome but I quite like Xcode. My main complaints are that the vim bindings are seriously lacking, and that it’s slow to start debugging when hitting a breakpoint.
Avoid using UIKit and Catalyst.