It completely mangled blocks in my site, which rely on both type-specific node templates (which it now seems to sidestep)
and also on CSS targeting the divs like:

<div class="div id="node-1455" class="node node-mine node-teaser node-type-page">

which it now seems to not even generate.

I've reinstalled 6.x-1.x-dev again and all is fine.