<< 2) Some folks appear to have a very different-looking UI compared to my trial version (3)... particularly Chipp Walters (I was following one of his tutorials last night). Are these customised, or am I missing a version somewhere?

Yes some advanced users have made some variations of the native UI with hard work coding!
Chipp is one of them! ;)
http://moi3d.com/forum/index.php?webtag=MOI&msg=7245.1

Max Smirnov is another one!
http://moi3d.com/forum/index.php?webtag=MOI&msg=6507.1
...

Of course you can use them and customise your own with their systems if the native UI is not enough for you! ;)

Or wait the v4 if there is maybe some new customized functions! ;)

PS Native UI has also some customised functions of colors variation!