I wonder if some sort of scaling (like top) would work.  For example:
   
   Discs  wd0  wd1  cd0  fd0  md0 raid raid               64 fmin
   seeks                                                  85 ftarg
   xfers  177  179                  35    3                  itarg
   Kbyte  11M  11M                 568  103              470 wired
   %busy 99.6 99.4                16.1                       pdfre
   
   Other things that come to mind are auto-scaling the widths of the
   columns based on the number of disk devices, and perhaps some heuristic
   to weed out devices that aren't really used (cd0, fd0 and md0 in your
   example).


yes please.  can you userlandize humanize_number(9) if it hasn't
been done so already or something? :-)