The national average for the new SAT is 1500, so any score above that is, by definition, above average. Whether that is "good" or not depends on the caliber of school the student hopes to attend.
According to the Princeton Review, given decent grades, a 1500 is probably adequate for a lot of four-year colleges, though it may not be enough to overcome poor grades or other deficiencies. If a student wishes to attend a top university, a score of at least 2000 is probably a more realistic goal. However, all schools have their own criteria and their own standards, and the SAT is rarely used as the sole criterion for denying acceptance.
Each section of the SAT is scored out of 800. Only about five percent of students score 700 and above in any given section. Less than one percent of test takers score perfectly or even near perfectly. Colleges usually set minimum standards for both individual section scores as well as a minimum standard for the combined score.