Re: Obviously...
What about the ecosystem of 3rd party tools and add-ons? are those going to be 100% compatible? I bet not, all MS stuff is intrinsically tied to a myriad of windows components.
Why wouldn't they be? They all speak Transact SQL over TDS. I've used Sybase Open Client (and more recently FreeTDS) to talk to MS SQL Server as well as Sybase. Granted, version of TDS does matter to some extent.