I will probably get used to it, but ... so much white. I am used to the subtle color variations between the main content area and the sidebars, and it helps me to intuit what is what and where to look for things. Even a hard rule betwen columns helps.
Also, as to Irish's note above, yeah, I think there is some intuition that expects us to go back to the forum/subforum we are in after hitting "Submit."
That may or may not be a niggling complaint based on what we are used to.
Similarly, the breadcrumbs at the top of a thread or a subforum, helping us get back to where we are, are in such a light gray that I am forced to peel my eyeballs to read. Can they be in a more contrasting color? Perhaps a Metly orange (xFF5910)?
Honestly, a lot of informational and navigational text is in that gray.