I use a 6mm marlow excel racing line. Has a very stiff braided sheath and spectra core. Its a bit overkill (3500lb breaking strain), but just right for size and durability. I payed $.32 a foot but bought 1200 feet.
I do not like the oem line at all, i feel it is distinctly unsuited to its task. The furling line is of much better quality. I recently bought a bunch of lines on ebay, found some decent stuff for $.35 a foot. Out of seven lines bought, one was super soft and useless on a boat. Otherwise, go to West marine or Defender.com. west has a much larger selection online and they ship free to the store or you can request a nonstock item be brought to your store.
2011 Golden Papaya TI with a 250 square foot spinnaker!
also a more manageable 100 square foot spinny...
the TI3 rear ama mod