Just for some tiny comparisons/highlights:
!). The fact that the last topic title takes you to the last unread post is a big bonus on all platforms since it doesn't require you to click on the really tiny icon that shows up next to the poster username.
Notifications all in one place.
The wrench simply contains a pop-up bubble of subscription options.
There are also changes in the UCP, MCP, and ACP but this isn't really the time for a full review. The above as well as some other differences highlight some of the positive changes that should make phpBB seem more "modern" by some people's views/standards.
Note the larger overall size which actually makes navigating around a bit easier. More so on a much smaller form factor such as a mobile phone. The beauty of this is that it did not require a separate style. The main style adapts itself on its own, which I think is pretty amazing (awesome job