The main function I will miss is the display settings option to have the board display the most recent post first on each thread, rather than the oldest. In other words I use the board 'upside down' and scroll down to go back in time rather than up.
It means far, far less scrollage
Also the simplicity of seeing the bold threads containing new posts in the list as soon as it opens.
I guess we'll get used to navigating the new one just as we did this one back in the day though. It's really just a question of familiarity I reckon.