Is it a fancy-pants upgrade of the base game? Is it a GOTY-like collection with the base game + Phantom Liberty + some additional content? I really love it when stores just put some vague bs in the description and you have to figure it out for yourself, because you're somehow supposed to know this stuff by default.

No additional content. The "ultimate edition" is just the base game + Phantom Liberty.

If you already own both Cyberpunk 2077 and the expansion, the ultimate edition adds nothing.
https://www.gog.com/forum/cyberpunk_2077/how_to_upgrade_cyberpunk_2077_to_ultimate_edition

I have both, but the launcher is still telling me to buy it. This is just like when I had my Xbox 360. I would boot up the console...and the first thing it would show me is and advertisement for the console I'm playing on. In both scenarios I'm being advertised something I already own. How bad does someone's amnesia have to be to boot it up, see the ad, and say "holy sh-t! I better go out and buy that right now!"?

I think this isn't some trick to buy multiple copies of the same game because the GoG checkout page will warn you about already having the extra content, and saying you can only purchase it as a gift.

Which launcher? GoG Galaxy? That is just a piece of useless software you do not need.

I'm running the game directly from the main .exe, and I have never been told to buy Phantom Liberty
...Apart from when I updated to 2.0, after having bought the expansion, but had forgotten to actually download and install it. *cough, cough* But that one is on me.

Not Galaxy, there is a separate launcher for the game.

https://imgur.com/a/tIr3hRT

It's strange you are not getting the launcher. I went to the game folder, double clicked "launch Cyberpunk 2077" and the launcher still popped up without Galaxy.

That is probably the Red launcher I've heard about. No, I don't have that one either.

I run Cyberpunk2077.exe, located in:
[X]:\GoG\Cyberpunk 2077\bin\x64

...and I just get straight to Cyberpunk 2077's main menu.

Sorry to resurrect this but I've just been looking at buying it and trying to work out which version to get. So the base "Cyberpunk 2077" is listed on GoG as coming with a bunch of extras such as the score, art book, digital comic, ect, plus some GoG specific extras. So the Ultimate Edition has none of the extras at all that come with the base game if you buy it on its own?

I bought the base game and the expansion separately, so I cannot speak with any certainty to what "goodies" are included with the "Ultimate Edition", but I would be VERY surprised if CDPR skipped every extra in the dual pack.

Having bought them separately, I got a "Cyberpunk 2077 Goodies Collection" (separate, time limited download) and "Cyberpunk & Phantom Liberty Goodies Collection" - and it's this latter one I expect you will also get.

It contains:
phantom liberty logo wallpaper 12 MB
cyberpunk 2077 wallpapers 716 MB
cyberpunk 2077 wallpapers (20th Anniversary) 1510 MB
NEW cyberpunk 2077 phantom liberty conceptarts wallpapers 2100 MB
NEW GOG exclusive cyberpunk 2077 phantom liberty wallpapers 1000 MB
phantom liberty key visual graphics 100 MB
phantom liberty wallpaper 61 MB
phantom liberty bundle wallpaper 44 MB
phantom liberty quadra vigilante wallpaper 19 MB
phantom liberty screenshots 841 MB
cyberpunk 2077 concept arts 375 MB
cyberpunk 2077 cover arts 626 MB
cyberpunk 2077 posters 1260 MB
cyberpunk 2077 screenshots 756 MB
cyberpunk 2077 gang graffiti 22 MB
cyberpunk 2077 steelbook arts 37 MB

There is also the sourcebook, soundtrack, avatar pack, digital comic and more posters listed as extras under the game installers. Which I also expect you will get.

But I don't know any of this for sure, just letting you know what extras are out there.

Was there anything in particular you especially wanted?
Any ingame item (weapon, mod, cyberware, vehicle and more) can be obtained through the CET mod console.

Soundtrack, wallpapers and digital comics would be nice. It's just £3 difference between buying them separately and buying the combined Ultimate Edition so it's not exactly going to break the bank, it's just why bother if everything is included in the UE anyway. Can't seem to find a list anywhere of extras included in the UE which is what made me wonder what was included.

If you end up buying the Ultimate Edition, and it contains none of the extras, I can whip up a .zip on my Onedrive if you want.
Though it will be several GB if you want everything.

Cheers, appreciate that, very nice of you. But it's fine - I decided to buy just the base game to start. I got that half price and Phantom Liberty was only £3 off anyway. I'll just take my time playing the base game and I'm sure at some point PL will be at least half price so I'll buy it then and that way I'll get it cheaper and I know I'll get all the extras anyway.