What do I need to know to run Linux as my desktop?

[techlists at phpcoderusa.com]

Had to move to Windows for business reasons about 5 or 6 years ago.  I 
see no reason that I cannot return to Linux on my desktop.

I use Ubuntu for servers so I am thinking of moving to Ubuntu desktop 
which is Gnome.  Please no flame wars.

My question is what do I need to know to run Linux as my desktop.  I 
know I will need to understand and have working knowledge of CUPS, 
however what else?  I am hoping to be able to get my scanner working.

What else?

I am using VirtualBox so I can do a trial run.