It's yet another rant, but there's a deeper problem with GUI "thrash" at Microsoft. One example is Outlook. The interface changed in 2010 and again in 2013. This causes confusion and doubt amoung users and distrust from IT and the folks that write the checks. Is the new software really better, or are the folks in Redmond just remodeling the interface to sell "new" versions?
I hope they're that smart. But I have a feeling they're just changing so often because they don't have any confidence in their abilities to design a good UI. On this basis, Metro has a couple of years before we see something completely different.