Why the change? Showrunner Steven Moffat explained at a screening of this year's Christmas special...
“I thought we’d been getting progressively whimsical with the interior of the TARDIS. And I started to think, ‘Well, why is that? It’s not a magical place. It’s actually a machine.’
“And actually potentially, as you’ll see more spectacularly later, quite a scary place sometimes. We make a lot of use of that.”
Personally, I rather like the new look. There's a nice nod to the classic look with the honeycomb in the background and the console looks like it did in the Tom Baker era. And the cool blue lights make everything look mysterious.
What do you all think?