I'm no great fan of the boring black brotherhood
but when it's done well, as here, it's classic.
The delicacy of the header logo font together with its powerful size - great.
Page title - categories - accurate priority and usefully clear spacing.
A generally clear, businesslike but distinctive feel where content is supported by design, not obscured by function clutter.
A slightly tougher, more hard edged version of the friendly, efficient XF culture. A good professional ID footprint.
The Search is wonderful placed up in the header - wish I knew how to do that!
My only single negative is the colour of "Search." As it's in a nonstandard place it will need to work harder to show XF fans where it is. For others it is high up in the gods so might trigger frustrated hunting lower down. I'd simply make the "Search .." text white to show the search function is there.