Okay, after an (admittedly brief) time with the new forum look I've got some feedback ready.
I think clearer delineation between posts would be helpful.
I think the pale green/gray color added to the sides of the "dimmed" style would make a better choice as the post background color and something even darker added to the sides. The stark white is too plentiful and is hard on the eyes. The old dark blue/light blue color scheme was easier to look at.
Font styles and sizes could use some changes. First, the size of the post text is on the small side. Second, more size differences between different elements would be helpful. Body text, signature text, and username all at the same size further makes the contents of each post run together.