|Hi Beer Hunter,
thanks for the kind words on the forum and for the thoughtful criticism. It is those thought exchanges that make the forum better. Quite a few of the participants have stimulated lots of improvements.
As for the ease of following a discussion: To me, the hierarchical view helps me a lot to see who responded to which message (although sometimes messages are posted as replies not to the message they are responding to but somewhere else). Others like PHPBB adopt a linear view and users try to make clear whom they are responding to by adding a @joe if they are responding to a message from joe. Well, the latter style is the one you see at most forums, since most forums use PHPBB or something similar. The disadvantage: less structure, the advantage: messages are ordered chronologically. To make it less frustrating for people used to the linear style, you can view a discussion thread in linear style by clicking the 'All' link.
As for registered users: At the moment, this forum does not require registration at all and therefore provides a lower entrance barrier. But I have to admit that you only can push what you can do that far without registration. E.g. user profiles are out of the question without registration. So maybe some day we will also have registration, hopefully only as an option.
The issue that responses to old messages can very easily be overlooked is a real one. Often, I tell people posting replies to old threads that this is the case and that they might want to start a new thread. But you are right: It would be nice to see the newest postings. There are some forums using a similar format like this one doing this.
As for sub-forums: Of course we can also do sub-forums. At another site where this forum software is in use, there are several sub-forum. I have to admit that in the beginning of this forum, I didn't believe that even this one forum would be viable. But now it is a place well loved by some. And sometimes, i even listen to improvement suggestions ... ;)