Leaks happen all the time and it is unsurprising that a video of the Windows Phone 7.8 update running on the Nokia Lumia 900 has been making its round on the Internet. If you recall correctly, Microsoft just recently announced via its WP blog that existing WP7.5 users will be getting the update in early 2013.
Here's the video, in which the resizable tiles feature is prominently featured:
In any case, WP7.5 users don't have that much longer to wait. To be fair, the WP7.8 update isn't exactly ground-breaking and feels more cosmetic than anything else. To recap, the update will have the following features: