You buy the hardcopy, stick it in computer, it asks you for steam account or whatever, so you make one and download it. Steam will then automatically update the game if it can, but it wont download the game if you own a hardcopy. Also make sure steam has remember password checked. From then you can backup and save the games files to your computer or whatever, so when you start up game whilst logged out of steam, it will ask you to login, you then hit play offline and it will allow you to play. If you can't even connect to steam once to activate it, then your out of luck.
GFWL makes you have to be signed in and online to even save games, so just be lucky you can use steam offline. The reason people have trouble playing games offline, is because they simply set it to play offline. The files need to be backed up elsewhere to work offline.
Steam also supports mods really well, so all those saying it doesn't are lying. I have Fallout 3 on steam, and i can play any mods just aswell, the folders are exactly the same, just in differnet locations.
Also if you don't want to have steam because you think its pointless, you will find it has its uses. You can get some really good deals and save up to 80% on some games, and before long you will find you are using steam more and more. Also as others have said, theres an in-game browser which is useful as you don't have to minimize the game, and if you don't want to use steam overlay due to a poor computer or such, just go into task manager and end it. It's simple.
I really don't see the fuss here, the only people that will be effected by steam requirement, are those with no internet connection to activate it, and even then i'm sure you can use a friends computer or something.
I do agree though that steam should be optional, but if it isn't, there really is no need to complain.