The update to BL3 was very smooth indeed using the the BL software release update process and everything still worked as expected.
Realising that everything working would not necessarily give me all the new features I then went through and created new templates using the values from my BL1.1 and 1.2 templates using BL3.
My approach to using Backlight is to try and use everything out of the box with as little recourse to editing PHPlugins or CSS as possible.
With each iteration of Backlight, more and more of the DIY stuff from the early days of CE through BL1 and BL2 have been built in.
When I get stuck, I hotfot it over to the ‘Forum’ where help is always at hand.