Its nice but...
Truth be told I think that having the ability to edit documents online can be very handy sometimes. I've used MS online web apps myself a couple of times now and it just works.
Still... In my opinion the real advantage here is having offline applications which provide support for online data. In other words; leaving the choice up to the end-users.
And IMO Office 2010 does an excellent job there. With the click of a button I can save my local data straight to an online storage (SkyDrive), and with the same ease I can reload it again.
But we should always realize; online work is pretty nifty; until the line fails and you're offline again. In such cases I prefer having the option to continue working instead of having to close the office down for the day.