I can't specifically address the 439, but I have sailed 4 SOs and 1 Sunfast ranging in size from 33-42' along the Southern California
coast and the one thing they all have in common is they are very comfortable for their size - in the cockpit
and down below.
Other than that they are all rigged differently so it depends on your preferences for winch
locations, key vs. keyless ignition, size of headsail, furling
main (with or without imbedded foot), transmission/throttle location, one wheel
vs. dual, jib
car track length, traveler vs. no traveler, etc., etc., etc.
For the most part, I would say they are nice, comfortable, easy boats to sail, but boats are boats; each with it's own ideosyncracies and things do wear out or break.
What other manufacturers are you comparing it to?