Will likely even open an own thread once I'm a bit more accustomed to the GT, findings so far (I'm sure they also apply to the GX in a pretty similar or even identical way, so it's not entirely OT):
Yes, onboard editing is dated, some things could as well be done way better within those restrictions. Heck, with 5 encoders per each block, *the* single most useful first page for an amp would be gain, volume, BMT, period. But it's model select, gain, sag, resonance and level. Wtf? Did they steal that illogical parameter order from HX land? Fortunately it's just the amps, all other blocks seem to have better sorted parameter lists, but still...
IR management and loading options are an abomination. Couldn't think of any worse way to deal with that. Don't even know whether IRs sound the same once converted through their utterly shitty tool. And why isn't there even a single hi/lo cut (or ideally lo/hi shelve) in the entire cab section? The included cabs would massively profit from that, too. Gotta waste an EQ as is - and while there's enough EQs, it's another block to select and jump between. Doesn't get more meh, really.
Fortunately, the internal cabs sound pretty good - but why in the world is there no way to find out which are the "original" cabs others than looking into some PDFs? Also, when exactly are the cabs switched when you select "original"? That's as intransparent as it gets. I mean, when you have 2 different amp models in that divder dual loop arrangement, when exactly is the cab switching? When changing Amp 1 or Amp 2? Maybe not exactly an issue because I will likely select cabs myself, but what a lousy UI affair, really.
As has been mentioned, block model selection is an utter mess. I want a list to open and want to be able to quickly see my options at a glance.
Can't believe their controller assignments are still as they were 20 years back. That's an offense to human intelligence no less. Their flexibility can hardly be beaten, though, and the CurNum switching option is just fantastic, that's really allowing you to get much more out of things, once you're used to it.
Soundwise, some amps sound just plain bad. That Juggernaut thing has to be among the least dynamic amps to ever live in the Boss universe.
Other amps are absolutely great. I could possibly live with just the Natural and X-Crunch amps until the end of all times, especially given that Boss' pre-gain-selection adds quite some flexibility.
Fwiw: Did anyone notice they seemed to have changed the amp's boost tone? It's a pretty high-midrange-y affair (true for all amps) where it was a lot more (but not entirely) neutral on the GT-10 - I vastly preferred that, even if I like some mid-bump for solos. But with the GT's boost, it sometimes even starts to sound telephone-ish.
The drives are the same, quite some mixed quality. But the Natural OD is something to save me everytime I need a grab-n-go thing. Great on its own but also doing very well in front of a driven amp. I absolutely love that Boss doesn't try to stick with the originals so each drive has a bass/bottom control, which is just super useful. I sooo often wish for that within the HX universe.
FX-wise, I just like Boss stuff. Always did. Yeah, nothing spectacular, but pretty much everything extremely useable and solid. Easy to dial in, too.
Time to get into more details and create a live bank (first job for the thing will be in 2 weeks, unfortunately I'm not allowed to bring it to the cover thing tour I'm currently playing, to replace the GT-10 they're providing there), so that's plenty of time to get used to things.