So office for iPad is a big deal and I think it's another signal in Microsoft's reluctant readjustment to the changing software landscape that Apple catalysed and Google has capitalised on.
The tight integration of Office into OneDrive mirrors the Google Drive and iWork + iCloud approach. Adobe is getting there too with Creative Cloud but my mate summed it up tonight; he can go to a coffee shop with his iPad, type some words, and his work is there when he gets home. Rich native clients, rich web clients, cloud backed storage. Your content follows you on whatever device you choose.
This is software in 2014, and it's exciting. Mobile, desktop, tablet, all converging.
Hats off to Dropbox and Box, these guys paved the way in cloud synchronised file storage but I have to doubt their viability long-term. Once Google Drive and OneDrive expose equivalent APIs for application integration, and if they can foster adoption in the same way Dropbox has, then I can't see these offerings lasting anywhere they aren't already incumbent.
The weak point is still revision control and collaboration; taking a leaf out of GitHub, Gist, SubEthaEdit and Google Drive would do all parties benefit.
Full client-side crypto is an area that still sucks from all vendors so it's still anyone's game, but it's a really great time to be a part of this industry.