You can delete a post of yours as long as nobody has replied to by clicking on "Actions" at the lower left.
The new design hides that options and forces us to make one more unnecessary click as we were used to.
But this design is a PITA anyway - too much cluttered so we are forced to scroll down heavily on every page and no way to get a simple straight clear overview. We have no chance to see at a glance who answered a post (we just see who initially posted). We cannot collect new posts from various places we are interested in. The streams don't qualify as an overview as one post blows up to about ten lines there so its pretty useless.
After one week of use I see that I continuously begin to use this forum less and less - its simply too cumbersome.