It claims lot of guaranties for your data (99,999999999% durability).
It claims to be secure against all natural and human destruction, despite being located in only one datacenter, 25 meters under the ground, in Paris, which means it could be subject to floods (directly or indirectly).
It claims to be able to handle formats that don't exist yet (for example, LTO-1 to LTO-10, the most recent version of the media being LTO-7).
It claims (with a footnote) to be able to handle "Secret Défense" data, which is extremely dubious. "Secret Défense" is the second most restricted classification in France. It's for highly sensitive information. Companies dealing with "Secret Défense" have to put many security measures in place (proper access control, separated networks, personnel habitation by the government, physical protection, tracking of every copy of every documents...) and are regularly audited by the government. The penalties for messing with that kind of data are pretty harsh, you could spend several years in prison if you publish an SD or just a CD (Confidentiel Défense) document, even accidentally.
Even if it's clearly targeting backup of state related data, it doesn't seem to have been audited by the ANSSI (french National Agency for Computer Security).
What is weird is that Online is a well established company (the parent company, Iliad is 4 billions euros in revenue).