Cold Turkey won't do
Not for any company that already has a nice big library of Office file formats. Maybe in an office of IT savvy that are not change adverse but if IT isn't the company focus it'll be hard making the change.
Libre may work for your PDFs (I'll have to try some of ours actually.. nice tip) but there are still too many formatting changes between Libre/Office file format handling. The way Calc and Excel handle cell formulas is incompatible (Excel has a fit when Libre/Open save the current tab into the formula) and your outright SOL if you've got staff using document macros. On the networking side, we'd also want complete Active Directory profile support on the *nix side or (preferably) a *nix hosted LDAP on par with Active Directory in terms of policy management and everything else above and beyond authentication (auth is easy.. ).
Oh baby though.. the day I can put a user in front of my *nix test rig and they can get all there tasks done.. oh I'll toss Windows like a turkey into a deep frier.
Good on you though if you can make it work seamlessly. Mint is a nice choice too.
