I haven't done any serious work in Blender since 2.49b ("I've been busy" and other assorted excuses), but I just installed 2.70a after reading this topic, as you've all reminded me how much I miss this kind of thing (context info: got degree in architecture, no jobs, became software engineer instead).
My initial assessment of the interface changes are "well ****, now I have to learn it again from scratch" and "it's hard to read," the latter being the only remotely serious one. Not a big fan of black on grey, and the various section headers just don't stand out enough. Font size is a little too small on my 2560x1440 monitor as well. Upon closer inspection, this all appears to be highly customizable, but I still think they could use a better default theme.
That said, my favorite feature in Blender remains unchanged: it isn't part of the Autodesk pseudo-monopoly, and thus I don't have to sell my car (or my soul) for a copy.