If you're not familiar with the story behind Open XML to date, Rob Weir of IBM has a decent overview. I'd be remissed if I didn't say he was somewhat biased, tho. An example of this is a comment he made about how he believes Microsoft will drive change in Open XML with every release of Office. This, in itself, shows how little he understands about the Open XML format and why its proponents believe in it as a superior format to ODF. I have no doubt Microsoft will try to push modifications as more and more customers ask for new and innovative features, but that's exactly why Open XML is better -- it was built with extensibility in mind, unlike ODF.
Here we are, waiting for the last leg of the process to kick off at the end of this month and some skeptics say, "While you're waiting [for the ISO decision on standardization], don't save in OOXML format." Should you listen? Probably not. There are some seemingly logical arguments behind the comment, but the position is flawed. He states that you should use the legacy binary formats to ensure a truly "open" experience. To word that another way, you should use a proprietary binary format instead of one based on open standards, such as ZIP and XML. I'm sorry, but I'll stick with my Open XML file formats, which I have full control over and can get data out should I need it, unlike formats like the legacy DOC and PDF formats, which require binary interpreters. I can get my data out of Open XML files without any document reader. I simply need a tool to extract the content and read text files -- not that I expect everyone to feel this way. Also, with more and more format converters out there, I fail to see the importance of constantly saving to a format your tool of choice doesn't natively support without translation. You'll get a much better experience working in native formats and only converting to another when you need to publish or share your content externally.
We're not looking at all bad news, tho. With the 3522 comments made on the original specification, most overlapping on similar concerns, 662 responses have been made. I don't know if there was truly that much overlap that would support 662 answers to 3522 comments, but you can browse the comments and responses online. In another attempt to ease the community into the new formats, Microsoft has also published the legacy binary formats.
What's perhaps more interesting is the fact that, in a truly independent study, the Burton Group found Open XML to be a superior format. You can get that report online, but I doubt most people will see it. Perhaps developers at traditional Open XML opposing companies like IBM and Google read it, tho, seeing as their products seem to support the new formats. Of course, I think this is a must-have. You can't have a tool that neglects the native file format for the de-facto standard when it comes to productivity applications.
What do I expect? I expect the format to be approved. I'd be lying if I said there wasn't a doubt in my mind, but the evidence is there that it's a superior format. The fact that these open source companies are so up-in-arms about Microsoft wanting to push its own formats thru the standardization process says something about their motives. Microsoft wants options and, with that, extensibility. If the format is judged on the merits, like all good arguments, the answer is clear. If you ask me, the worst thing about Open XML is Microsoft's name on it. If that weren't there, it'd already be a standard.