Thanks Stabbey for the quote, I searched the forum but didn't see it.

OK so there actually IS mandatory steam on boxed version, and it's a real problem for me.
Having many internet (and Steam) problems, this decision bugs me a little bit. Yeah, I have access to a GOG backup copy, but isn't a real good solution as game files are usually too big to be downloaded easily for me...
I understand their point (version written on DVD wont be final, extra content will need to be downloaded, as Ubisoft did for MMX), but I still don't get why did they claimed to have "no DRM on box version" and did that. Patching a "real" DVD version is (for devs) quite the same thing as patching a GOG/Larian Vault version AFAIK, isn't it ? Just release patch files on official website and let's go.
I don't know if I will ask for a refund (God knows how much I want this game^^) but... it's a problem. Next time I'll wait before I buy^^