I have a curious question.  I'm dating a wonderful man who is a Sagittarius.  Every 'compatibility' chart I've seen says that we will have a difficult relationship.  (I'm a Pisces) and yet, we've had nothing but smooth sailing and wonderful times.  We've been dating for almost a year now.

I took a quick peek at Scorpio and that description fits him more.  Since his birthday is Nov 27th - 6 days past the date 'cut off' - I'm wondering if it's possible for him to be more influenced by the Scorpio sign than the Sagittarius sign?  If that makes sense at all.

If his moon is scorpio, then that would make his basic emotional nature more scorpionic. Also, if he has a lot of planets (including his sun), in the 8th house of his natal chart, it can give him scorpio influences, since the 8th house is ruled by scorpio.
You would have to look at the whole chart. I'm the same as him, except I'm a virgo with a scorpio moon and 8th house sun, venus and mercury so I feel my emotional nature is much like a scorpio
Do you know his birth time and place? If you pm me those details I could take a look at his chart for you
Oh, and never look at suns for compatability. I find the moon to be more important here.