Post islands are basically small blocks that contain recent posts or topics. You can see one in use here on the left side entitled "Recent Topics".
Yes, you can create an RSS feed for a specific forum or for multiple forums.
You cannot search inside an individual topic at this time.
Rating a topic is under the "Topic Options" dropdown. Rating a member is done from their profile screen.
To add more things besides each post would currently take a template modification, would be fairly simple and could be requested at ubbdev.com.
Yes, you can make 5 custom profile fields. These can be setup on the Registration Settings -> Registration Screen Tab in the control panel.
Show user avatars for anon users is set under Display Options -> General -> Topic Display Options.
You can't rate individual user posts at this time. Only the user or the topic itself.
