To be honest, I don't see many traffic tickets for u-turns.  But, I do occasionally see improper u-turns claimed as a basis for stopping someone who then gets charged for a more serious offense, like DUI or drug possession.  So, it is definitely worth understanding what the standards are.

What we call a u-turn requires a little more description than that in the statute.  OCGA 40-6-121 describes it as a turn "so as to proceed in the opposite direction."  There are four situations where such a turn is prohibited.

• On a curve.  U-turns are prohibited in any curve.  Even though it says "any curve", It would be unreasonable to most fact finders to treat a slight deviation from a straight line as a curve where a u-turn could not be performed.  On the other hand, if one sees a sign like this you probably should not be doing a u-turn.
• Near the top of a hill.  "upon the approach to or near the crest of a grade where such vehicle cannot be seen by the driver of another vehicle approaching from either direction.  Again, there is a fair amount of discretion built into that description.  A reasonable interpretation is that we are talking about an approaching vehicle within a close enough distance to be effected by the u-turn maneuver.  
• Where a prohibition is posted.  Basically, are there signs?   If there are signs, you are definitely inviting a stop or a ticket if you proceed with a u-turn.

Even so, I see many situations where officers believe that u-turns are illegal even when these conditions are not present.  They are not always right about that.  That said, civil law is likely to be less forgiving of the driver performing a u-turn where a wreck occurs.