I'm running version 16 on a 64-bit computer without major issues (only sharing to PDF causes the program to crash, printing to PDF works fine).
On the other hand, 2012 is better than 2006 in many ways but some features are not the same and the program will not run as fast as the old program (screen updaets are slower, reports run much slower, etc.) I would not go back to the older version but use it when needing to look at old files that I do not want to convert to the new format.
If you do not like change, you may not like the new version. I've posted a screen shot of 2010 for your reference (1680 x 1050 screen resolution.) You can see how the screen is laid out, etc. You enter facts for a person on the right hand side pane or in the "Person" tab above.