Niner since 2012
LOL--cursor dancing to Grapes!
I've always found MEF (and DI/IOC) to be ironic.
It's useless until you need it, then it's indispensible!
First, ditto on the obscurification via gray buttons.
And, on the plus side:
1. The temporarily open preview tabs will help me reduce "tab clutter".
2. Including powertools natively is great no-brainer...especially Solution Explorer.
3. VS now being single-instance/multiple-context is useful (yes, I've opened 3 copies of VS at once).
In the too-soon-to-tell category, debug navigation in the solution explorer could be more intuitive as long as it's really as flexible as I imagine it to be.
Overall, I like the emphasis on "keyboard centric" vs "mouse centric" use of VS tooling.