Thanks for alerting us to the update. I think I have experienced the definition of irony -- in order to install the update and experience the improvements in battery life it first told me I had to...
Like wandered (and lots of others reviewing on the Windows Phone Store) the Solitaire Collection is a battery and CPU hog on a phone (mine's an 8X but other reports are on 920s) -- makes the phone...
8 to 8.1 keeps everything, including apps.
8.1 Preview to 8.1 keeps data but you have to reinstall your applications.
I agree with noirsoft:
Paul Thurrott's Field Guide to X for a large book
Paul Thurrott's Pocket Guide to X for a small book
Makes sense: that looks like Exchange 2013 OWA.