ZFR: Well, so I decided to buy the anthology. Here are some notes, if anyone is interested:
_It's more or less like GoG. The games appear in your library and you can download them DRM free. You get the free games as soon as you sign up.
_Games are bundled with Dosbox. The configuration seems to work ok. If you want to change anything, you have to change the dosbox config file.
_Manuals are there (I haven't checked all games, but they were there for the ones I checked). There is no link to them in the start shortcut folder, but they are easily located in the install directory. Pdf format.
_NO extras seem to be available. For example the shareware, extreme and rejected extra levels of Rott, don't seem to be found. They were there on the old 3d Realms website.
Overall:
I already had some of those games, the ones I was most interested in. However, it did have some games I don't own and would like to play, notably Shadow Warrior. The ones I didn't have were worth about 65$ if bought individually, out of which 40$ were ones I'm interested in. I think it was a good deal.
I believe/hope the extras will be made available later as soon as they complete the move to the new website. They were there on the old site anyway.
Thanks for checking that out. I plan on buying everything there, because Apogee was my gaming childhood. I do hope they bring back all the content missing from the original site, like the cheat codes section, as well as all the extra download material. So when you buy the anthology, it's not just one product on your shelf, but it unlocks all the games so you can download individual installers? And there's definitely no extra levels zip or anything anywhere in the ROTT directory?