What's new in v3?

Hi

I'm an occasional CI developer, my last app being developed in 2013 under CI v2.0.4. Returning just now I see that v3 is current, and v4 on the way. Could someone point me towards a doc or forum post with the major differences between v2 and v3? There are plenty of very detailed changelogs and upgrade paths, but I'm really just after an overview. At first glance, the main differences I've seen are:

a) Active Record is now Query Builder
b) The documentation is no longer the 'tab' dropdown (a shame - I rather liked that)

I did a Google search for "what's new in CI 3" but only found docs such as What are the differences between CodeIgniter 2x and 3x? which is very much at the tree, rather than the wood, level.

No big, but if there are any major changes it might be useful to know about them before I get stuck into development.

Fred