If you're a small company sans the patience to wait for Windows 'Live' Office or the desire to switch to Google Apps, then Syncplicity in particular looks the way to go. Mind you, presumably Syncplicity will get gobbled up by Microsoft so it may not really matter either way.
If these guys don't get snapped up anytime soon then their real future could lie in not just seamless syncing, but more importantly syncing seamlessly between platforms and disparate applications. I.e. Mac to PC to Linux box and out to Smartphones - shifting MS Office to Apple Works to OpenOffice etc. Bingo - Nirvana!