Yes, I have for people at work, but thus far only when Linux and Windows are installed on separate drives. That's not to say that Windows and Linux can't be made to co-exist on the same drive, it's just that we haven't had the reason to try
The easiest way was to install Windows first to the primary drive, then install Linux on the secondary and use the boot manager of your choice on the MBR of the primary drive. We did it with lilo (lilo can work with ext3, contrary to what some believe).
We also have some Asus mainboards which make it easy to select your boot device by hitting Esc during the POST..