While the look certainly isn't flashy, I'd be fine with the look. It's the reliance on 3-button mice that's a problem for me. At least modern laptop touchpads can do middle mouse click with 3-fingers but that's a pretty lousy UX, so it's really only practical with a real mouse.

Also I'm much more of a keyboard + tiling window manager kind of a person, so the plan9 focus on the mouse isn't my cup of tea.