This is seriously cool technology
Edit 1st Feb 2015: No more drawbacks. Microsoft have released more apps which now make MAM a very good feasible solution.
(Edit 1st Feb 2015 - My view has changed now with the release of Office apps for Android)
Microsoft Word for iPad
Microsoft Excel for iPad
Microsoft PowerPoint for iPad
Microsoft OneNote for iPad
Microsoft Outlook for iPad
There are more useful apps for iOS. However the Managed Browser has not yet been released. It is currently pending store approval.
Also Microsoft have released an iOS Wrapping tool with which you can enable your own apps to be managed without any software development. I'll investigate this tool shortly.