I currently am using Apex, which I'm finding perfectly useful. I don't believe that TouchWiz supports a 5x6 layout grid, does it? That was my primary reason for switching. That and the backup/restore homescreen feature.
As far as S-Pen functionality, I still get the notification when the S-Pen is removed and S-Note automatically pops up upon removal. I don't get the Pen apps menu, but then again I never used it so I don't miss it...