I just started using YaBB SE. I think you've done a nice job with it. There are a few concerns I have, though.
The first thing is I had to hack the php files to get my board to look right. For example, the table that contains the information:
QuoteTopic or subject goes here
« on: December 03, 2002 11:45:09 »
isn't the same color as the background of the post unless you set the table to have a transparent background. If you do that, though, you have the border color showing through and so on. So I added a table.clear class to the CSS so I could have some of the tables transparent and others not.
The other big problem is with the font for the "code" is hardcoded. That needs to be in the CSS, too, unless there is a good reason for it to be hardcoded.
Quote<td class=quote><font face=\"Courier new\">
A suggested feature I would like is the option to have the "Recent Posts" section show only titles instead of the entire post.
All of these things are really minor issues. You have created very nice forum software and I'm very happy with it; YaBB SE is definitely among the top (if not the top) free forum software available. Please keep up the good work.