I really like how the new forums look and fell. The extra level of information, like the people involved in any particular thread, easily visible activity dates, etc. and minimal layout just feel great.
Also, having the ability to use a dark theme is just great. It is so much easier on the eyes and makes late night browsing more pleasant. 
However, the one thing that I am probably the most fascinated by are the badges. They are a relatively small thing, but I would expect that there are more people like me who are already thinking to themselvesā¦ āGotta catch 'em allā while the original Pokemon theme plays in the background.