This.
The last company I worked for had some very seasoned Linux people, and shipped a half dozen Linux servers (pre-loaded with our software) a week. The developers ran Linux; the office staff ran Windows and OS/X.
We the developers had to tweak and fiddle with our boxes for a couple of days every single time the AD server was patched or updated. We never did find drivers for the colour printer. Only one scanner out of four would work for us.
We had to run Linux in order to do the development for the servers we shipped, because each developer's workstation was an in-development image of the server software.
But from an administration and overhead position, it was a freaking nightmare.
I run Debian at home on one box, and Windows 7 on a laptop. I don't have problems with it because all the hardware I own was specifically chosen for Linux compatability. I don't have AD problems because I just let the Windows box access read-only Samba mounts from the Linux box, and don't map my drives in reverse.
But there is no way in hell I would ever recommend a shift to Linux unless it was for the entire company and they were willing to bankroll the time and effort it would take to properly set up Linux-centric file and print services.
It's just not worth the pain.
Whatever you save in licensing and hardware upgrade costs will be eaten by tech support costs in six months when you're only doing a partial/small-scale migration such as is being described.