Style sheets: woohoo! glad to have them back. Like I posted on one of those threads, you could implement quite a bit of your original beta in CSS, and allow users to change that to their preference (colors, fonts, etc.)
Sidebars: love 'em. The best change from the old style.
PHOTO ALBUM / Image Hosting: Sounds good for the hostless folks, but do you have unlimited bandwidth? or some way to throttle popular images? Anytime I hosted an image it got hundreds/thousands of hits, and really sucked down my bandwidth.
I can't seem to find the 'My Subscriptions' link to tweak the number of threads listed in each sidebar topic?
Also, do you have a list of the various CSS classes you use. A little shorthand crib-sheet would be handy when rolling our own.
Great job, I really like the layouts and colors in your original beat. I will play with this this weekend (and maybe build my new computer to play with it on).