Welcome, and grats on your purchase!
Even though mine is back for repairs, im still one of those "fanboys" that just thinks it's awesome it seems
To prepare i would suggest you look if the platforms you own games for (don't ask for roms and stuff here) have a proper emulator, and if they need a bios. That will save some problems.
After you receive it you will want to install the latest hotfix, and also the codec pack with mplayer for multimedia stuff. I think it's safe to pre-download the codec pack, but i'd wait with the hotfix until you receive yours. If you just ordered, might be a while until you receive it, but you know that probably.
Beside that, it's pretty much ready to use when you receive it. Just pre-download some game and emulator pnd's and you are ready to go
Cheers!
Edit: keep in mind though that improvements are still continuously made to most software. If you download everything now, a lot will be outdated when you receive yours. Make a selection of the stuff you like now, and download the latest versions when you recieve your shipping mail seems sensible. That, and get your roms/images/media sorted the way you like
