I use only the desktop version. I don't see any difference in functionality, only appearance. I think that the orange buttons are silly and obnoxious, but I can live with them. Just out of curiosity, why? I do note that the first button in the row is orange, regardless of what it says. That doesn't make sense to me.
Orange buttons get a little darker on rollover, but some of the blue buttons don't. And of the blue buttons that do change color on rollover, some do it differently. Within a post, rollover changes the color slightly. But when entering a new post, the "Submit Reply" and Preview Post" buttons reverse colors on rollover.
The yellow shading for announcements is an improvement, IMO, makes them easier to see and distinguish from regular threads.
The "View Next Unread" oval button at the bottom right doesn't size correctly, and cuts off the lower left of the first letter of the next thread title.