I have been using 3.3 as a basic tool for the best part of a year, the 3D part of it for only two or three months. We have now switched over to ADT 2005. You are correct there are yards and yards of hidden tools and routines.
I would suggest that you take time to set up office standards as you go, such as standard wall, window, doors, tables etc. Set these up in an office tool pallet.
Take you time. Depending upon you building type, you could start by simply producing 2D plans (yes I know they are 3D but you don’t need to look or consider them as 3D). Produce schedules of doors, windows, furniture, etc, much as you would with 3.3.
The sheet manager looks exciting, although I am yet to use it.
Oh, and get a second screen to keep the tool palettes and all of the other information that you will need.