There is little consensus on the board about the preview courses. Many people think them an absolute waste of time and money, and seem to hold that opinion rather strongly. They make very coherent arguments against any useful learning on the subject matter taking place. They make the point that any advantage the course might give you will have long dissapated by the time exams come around.
However the proponents of the courses make the points that the benefit from the courses isn't the subject matter, but rather the "how to study/brief/outline/time management portions of the courses. They seem to feel that an a feeling of preparation and confidence may help them adjust and get 'in the groove' faster. It is repeatedly pointed out that it may be of more advantage to someone who has been out of school for a while.
The proponents of the courses seem to lack credibility in the sense that they all seem to be people who have spent the money and are trying to justify it. The detractors lose an equal amount of credibility in that none of them seem to have actually taken the course. Law students I know who have taken the Law Preview course said it helped a little at first, but probably didn't make any difference by the time exams rolled around. No one except the companies that take your money are emphatic that it will make a difference beyond the first few weeks.
I think it all comes down to how you want to spend your time/money. People scream about how expensive a $1,000 course is at the same time they are borrowing $120,000+ to pay for school. They talk about wasting your whole summer by taking a 5-day course.
I think it probably is a bit of a rip-off. BUT what have you got to lose. The cost is absolutely inconsequential compared to the cost of attending law school. The time is five days out of a 12 week summer.
If you think it will help you adapt, cope, get started on the right foot, whatever... Then I say do it. Most peple seem to regret the things they didn't do more than the things that they did.