Here is the plone 5 presentation I put together for pycon-my.
I tried to summarise what I think are the killer features. Instead of the 3D's which was the original strategy from ages back, it came out as 5E's.
- Easy to theme
- Extendable
- Easy to use
- Enterprisy
- Extremely hard to hack
A lot of the marketing I've seen around plone 5 hasn't emphasised theming as a killer feature. Not only is there a clean theme to take and modify using a very simple non coder friendly language, but we now have a great story around how to include inplace editing with the toolbar by only adding 2 lines to your theme rules file. If you can't theme a CMS easily it's useless IMO. We complete well with ExpressionEngine or Craft CMS in this regard but almost no one knows it.
For plone 5.1 I'm hoping we can add "easy to get started" to that list with out of the box prebuilt site examples, distributions and SaaS (see https://www.ostraining.com/blog/general/predictions-for-2015/)