Larkware news gets to the heart of the matter on the "big announcement"

I worry about the smaller file sizes business, too. Are smaller file sizes really all that relevant in these days of rapidly-expanding bandwidth and disk storage? When was the last time you ran out of disk space because of the size of your Word documents and Excel spreadsheets? (Now, the size of your Visual Studio install, that's another story). It looks to me like the smaller size comes at a cost: "The smaller file sizes are enabled by a combination of industry-standard ZIP compressed files technology that automatically compresses each component within the file as well as the reduced overhead of an XML format." So, you don't actually have a pure XML file to work with; you have a zip file containing a batch of XML stuff. This raises the bar in terms of the tools you need to actually interoperate with the new formats. It's not going to be as simple as just plugging them into the same XML tool stack you use for any other XML file format.

Yes, sticking a bunch of XML docs into a zip file doesn't exactly make it a simple matter to "just plug in your existing XML tools". What we've actually got here is one sticky tarball (existing Office format) replaced by a new sticky tarball - the big difference being the word "Open" slapped in front of it for marketing purposes. LarkWare examined the license and came away thinking it was pretty opaque - you should read that yourself (IANAL). This riff is good too:

So what's the bottom line? Well, XML is nice, sure, but honestly, most users will never care. I don't care if you save my document in XML, Braille, cuneiform, or chicken scratchings, so long as you can get it back when I ask for it. Some tool vendors, who can puzzle through the license and handle the legalities, will find their jobs marginally easier. Microsoft will have an additional flag to wave at confused legislators the next time open-source advocates argue for a switch to non-proprietary software ("Look, even the name says we're already open!"). All in all, I see this as a nice PR move, and an interesting technical achievement, but not of any particular significance to most users of Office.

This is 90% PR, and maybe 10% meat. It worked, too - they sure got a lot of undeserved attention out of a nothing-burger announcement. Now maybe if they had announced that they were supporting the Oasis Office Document standard...