Welcome to the family.
Firstly, get SkyDrive. Its very important, as a wp user you get 7gig of "cloud" storage, that is to say you can store 7gig of data on the Microsoft servers.
Your picture hub and office apps will auto snyc with SkyDrive and allow you to have your pics and documents saved online instead of your phone. This saves space.
SkyDrive also interacts with audiobook apps, emulators, picture editors and such allowing you to listen to remotely stored books, edit online pics and play supermario on your phone. These are non exhaustive examples.
Group tiles is a great app that allows you to make dummy or header tiles for you to group apps under. For eg, i have media, games, news and tools headers and the relevant apps then pinned under them.
Pinning is when you add something to the home screen, this is usually apps, but you can also pin youtube channels, web pages and albums or playlists.
I'm sure lots of people will chime in with great advise, so that's a good starting point. Oh, get metro tube or mytube, they are the two best youtube apps.
The good news is yes, the htc 8x will indeed get 8.1