Morgan is back with part 2 of his developer blog (part 1 is here).  He talks about the subtle and not-so-subtle changes they've been working on, including the new "hover up" ability.  

Unlike the obvious appeal of rocketing around with a jetpack, "hover" might not immediately sound sexy, but if you think about it like a game designer, it's actually pretty revolutionary.  Being able to hover up (or down, or left, or right) basically makes every part of every area accessible.  It adds a lot of fun, but also creates a lot of challenges in terms of creating level flow, maintaining difficulty, etc.

Rather than hearing me try and talk about it, head here and just watch the video. It gives a great sense of the real freedom and verticality of the game--you really can go just about anywhere and approach a given situation from any angle you like.