I haven't used this myself, but heard people who have used it talk about the software in the highest terms. Also, it appears that MS-Office format compatibility is far better than that of OpenOffice. Also, they sell professional fonts for Linux, too, so that alone will probably make the whole thing look much better. This may go a long way on its own.
Perhaps if you test drive this and show it to your boss, let him play with the Windows version for a while to prepare the ground etc etc, you might just get lucky and he might be more open to discuss Linux thin client deployment with the Linux version of them Softmaker folks' software as an alternative to MS-Office instead of OpenOffice. It may be worth a trial, I guess.
Also, how about running MS-Office via CrossOver on a Linux box. Not acceptable to your boss?
anyway, good luck.