this is a very useful plugin, thanks. I have two comments:
1. The read and unread icons are very similar. It would help a lot if there was some alt text with them. I had a quick look at the code, but couldn't work out how to add it to the particular line which displays the images.
2. The 'mark all topics as read button' does, rightly, disappear when you use it. But if you then view some other pages and return to the forums, it reappears, even though there are no unread topics. It's not a major issue but could confuse some people - it would be better if it appeared only when there actually were unread topics.
Thanks again for the plugin.