At least two people said, paraphrasing "I like how it looks with long posts, but not with the shorter ones". SMF allows specifying a default per-subforum theme in the admin panel. You MIGHT want to consider making both "old" and "new" layouts available (that'll also alow people who don't like it to switch in their profile) and set up the "new" one in the writers subforum only.
Just trying to be useful... I like the new one, the only tweak I'd propose is increasing the margins somewhat. 4-6px larger margin fo the sides of the post contents, and 8-10 for the signature. Especially the sig starting so close to the edge of the layout looks a bit ugly. (It's only my opinion.)
Please note that I use "margin" here in the general sense... padding might be more appropriate technical detail to use, dunno.