One thing we know as of right now with Windows Phone 7 is that customization will be drastically limited. At least until the folks at XDA figure out to root and mess with the OS.
An example of what customizations you can do will be the use of "themes" which is a generous description for changing some font colors and accents. Yeah, basically it's not much. One example is in "Pivot" (below) the other "Panorama" (above) which are two of the formating options for programs by developers.
Still, it's better you know now what you can and can't out of the gate then later. So commence logging your complaints in comments...now.
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Daniel Rubino is the Editor-in-chief of Windows Central, head reviewer, podcast co-host, and analyst. He has been covering Microsoft since 2007 when this site was called WMExperts (and later Windows Phone Central). His interests include Windows, laptops, next-gen computing, and for some reason, watches. Before all this tech stuff, he worked on a Ph.D. in linguistics, watched people sleep (for medical purposes!), and ran the projectors at movie theaters because it was fun.