There are two things that mess up the forum UI in a big way imo.

First, if you change the title the reply will not be in the tree. Anything with a changed title is not considered a reply. It is a new post in the same thread. This is totally at odds with what we have become used to

Second, if you use the box at the bottem without clicking on reply, your post will not be in the tree. There is a natural tendency to use the available box for reply without actually clicking on reply but it screws up the tree

If those two things could be fixed, the interface would be very similar to the old place, espaecially if you choose the headers only option

I don't know how the flash thing would work out. I assume it would be a much richer interface than the test run on geek.