But some organizations may want their data to go into a separate app than where your personal data goes, for the usual old-school fears about corporate data loss in a world where they nonetheless want you on call 24/7. And the OWA app can be configured by IT to require the use of a passcode, which makes it slighty more secure than the native clients, which don't. Just remember that the native clients assume you have a passcode on your device, which IT can easily enforce through Exchange ActiveSync policies from the Office 365 Exchange admin tool.
This separation may be desirable as a user, as it can create more separation between work and personal, a move many "work anywhere, work any time" users could benefit from. If Apple Mail or Google Email don't display your work messages in the evening, because work email goes to OWA, maybe you'll be less tempted to answer them after hours. iOS, OS X, and Android can be set up so that your work email goes to OWA and your personal email goes to the native client, but all your work and personal calendars display in the native clients for a unified view. In other words, you can mix and match the separation.
Connectivity woes plagued our deployment
It's hard to tell whether this is an issue with Office 365's service, with the complexity of its setup, or the skills of our Exchange-experienced IT department, but Office 365 has been plagued with connectivity woes, which seemed to hit non-Windows users disproportionately. For example, when signing into OWA for iPad, some users had to wait a day or two for the credentials to register, although they were already enrolled and active in Outlook or Apple Mail on the Mac.
Although users like me could access SharePoint and OneDrive for Business from our iPads using the OneDrive for Business app and the Office for iPad suite, we could not do so from the Microsoft Document Connection service on the Mac (that add-on to Office for Mac is an amazingly bad hack, by the way). There is no OneDrive for Business app for OS X, so that can't be used as a workaround for the problems in creating a direct OneDrive connection from Office for Mac. Instead, you have to use the OWA service on your browser to access your business OneDrive account on the Mac.
Connectivity problems wren't limited to file access. Perhaps one time out of four, OWA for iPad has trouble connecting to the server, resulting in signin delays of a minute or more. My EAS connections to the Exchange server feel noticeably slower than they had on our on-premises Exchange server, whereas OWA is much faster -- that may have to do with a lower limit on simultaneous EAS connections in our Office 365 deployment.
Then there's Lync, Microsoft's conferencing service: According to multiple users here, Lync on the Mac and iPad is frequently crashes or loses its session connection. We employees did what any modern company's employees do: We reported the bugs, we heard IT tell us they didn't experience the problems on Windows, then we got our own tool (Citrix GoToMeeting, in our case) that does work on all our devices. I'm not sure Microsoft yet understands this reality, given its standard sales pitch to IT is still very much about control, rather than to users about usability.
All in all, Office 365 feels rickety when it comes to connectivity and interoperability. My company's operations team that hadles Office 365 says bluntly that the issue is that Microsoft's compatibility with its own services across platforms is poor, with OS X and Android particularly shortchanged. It's raised the issues with Microsoft in hopes that Microsoft will level the playing field.
What about Android, the iPhone, Windows Phone, and Windows 8 tablets?
Microsoft's new CEO, Satya Nadella, has hinted that a version of Office similar to Office for iPad is being developed for both Android and Windows 8's Metro environment, which is what Windows tablets are supppsed to run as their primary OS. The fact that Microsoft delivered Office for iPad before Office for Windows 8 speaks volumes about Windows 8's failure in the market.
The fact that Microsoft hasn't gotten around to Android Office likewise reflects the truth that Android tablets are rarely used for professional purposes; they're basically entertainment devices, and even then by a small percentage of people. Much of the claimed market share data for Android tablets is simply bogus -- Samsung has been caught several times misrepresenting its sales figures, for example -- or reflects what are actually e-readers such as the Amazon Kindle Fire and the AOSP-type tablets popular in poorer nations, not Android tablets that have plausible business use.
That leaves smartphones. Apple's iWork works very nicely on an iPhone, but Microsoft's Office for iPhone is a barely functional text editor. Microsoft Office's Android version is similarly unusable -- as is its Windows Phone version. For now at least, Microsoft doesn't believe people will use anyone's smartphones for serious office work, so it's not trying to deliver there.