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 for
steering 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?