What could be simpler?

gistfile1.sql

MERGE INTO  vegetation.PlotHeader AS Target
USING       (VALUES(@PlotNumber,@SurveyDate,GETDATE(),@ProjectId,@PlantCommId,@Comments,@PlotId,@NorthShadePercentage,@EastShadePercentage,@SouthShadePercentage,@WestShadePercentage)) 
AS          Source(PlotNumber,SurveyDate,LastModified,ProjectId,PlantCommId,Comments,PlotId,NorthShadePercentage,EastShadePercentage,SouthShadePercentage,WestShadePercentage)
ON			
(
  Target.SurveyDate = Source.SurveyDate AND
  Target.ProjectId = Source.ProjectId AND
  Target.PlantCommId = Source.PlantCommId AND
  Target.PlotNumber = Source.PlotNumber
)
WHEN MATCHED THEN
  UPDATE SET	
        LastModified = Source.LastModified,
        Comments = Source.Comments,
        NorthShadePercentage = Source.NorthShadePercentage,
        EastShadePercentage = Source.EastShadePercentage,
        SouthShadePercentage = Source.SouthShadePercentage,
        WestShadePercentage = Source.WestShadePercentage
WHEN NOT MATCHED BY Target THEN
  INSERT (PlotNumber,SurveyDate,timestamp,LastModified,ProjectId,PlantCommId,Comments,RowGuid,PlotId,NorthShadePercentage,EastShadePercentage,SouthShadePercentage,WestShadePercentage) 
  VALUES (PlotNumber,SurveyDate,DEFAULT,LastModified,ProjectId,PlantCommId,Comments,NEWID(),PlotId,NorthShadePercentage,EastShadePercentage,SouthShadePercentage,WestShadePercentage);