If the small print says all the promotions you have will stay, what is all the fuss about?
If you were given stuff (I was given 25GB (15 + 10 loyalty I think) + 15GB (Camera roll) + 200GB (Surface purchase- two years), then you get to keep it (at least as long as they said).
I presume the 'unlimited' wasn't a promotion per se. I am surprised there wasn't small print at the time along the usual lines of "Fair use policy applies", the same as so-called unlimited broadband. Albeit a bit different since the storage stays there and MS have to keeps multiple copies of vast quantities of data.
I suppose they could technically keep their word and put the enormous data on tape/disc in archives with slow retrieval (at least latency-wise, it would still keep up with most peoples' DL speeds).
The thing is, you can have it both ways, OneDrive is just a directory. If you PC has a HDD or larger SSD then all of your OneDrive is also on your disc (or vice-versa) and File History or good old backup makes a regular copy to an external hard drive. File History has the added benefit of keeping all the versions of changed files, albeit without the elegance of a version control system.
So, there are three copies if you count the OneDrive as a copy. You can access files elsewhere if you have a connection, all of them since you do not know if you might need that picture or spreadsheet (or just want rather than need) but while maintaining total ownership and control of a real copy locally.
And, as an added bonus, those people with lots of photos get the added ability to search them by tags. I was looking for a photo of a piece of paper I took a some stage and clicked on the 'text' tag, which reduced the photo count to a reasonable eyeball search.
Furthermore, any text itself is searchable (a pub name for example or a museum pic with a description plate or a car number plate).
You can also present the photos such that they are separated by location as well as time which can be useful too.
Finally, you can search for 'car', 'house' or 'people' and similar generic terms and it will find pictures with those items in them, pretty well from my experience. This even works on the phone which is by far the most useful reason to have it since scrolling and searching massive photo collections can be a pain. I do create folders etc. myself but it is surprisingly easy to not bother - I do it mainly to share.
As for sharing, any arbitrary search result or manual selection can be shared as is. Even if the photos are subsequently moved or renamed, they stay shared.
These are all things which a straight backup cannot do although I suppose there may be apps they will not be as easy to use for sure since I can take a picture, it uploads automatically, it is tagged and searched for text without any effort at all from me and can be shared trivially - the data I send is a link, they download it from the servers.
If you share via the server you must run one to do so, then your upload capability is supplying that bandwidth, especially if it is a popular video. You also have to maintain the share system, knowing who has what etc. So what you probably do is actually have a service you use to share, dropbox etc. You copy the files required to that place as required and share afterward just like normal cloud users.