I have heard both good and bad on both BarBri and LawPreview. Search the board for either one, there have been a number of discussions on both. I know a lot of people think that it's a waste of money, but I think there may be some value in just becoming familiar with the subjects and exam methods. Can you learn all this stuff on your own from books? It certainly seems so. Will most of us put the nose to the grind all by our lonesome and get maximum use out of the materials we CAN purchase? Eh, that's debatable. I think you have to ask yourself 1) if going to such a program would put you significantly more at ease upon entering law school (the possible psychological benefit is real and might be worthwhile for some) and 2) are you comfortable with and prepared to give yourself the same kind of overview that the program seems to give you.
Of course, it's a balance with the costs. If it were free, then it would be obvious (after all, surely the programs can't hurt!) I'm leaning towards one myself, primarily because I think I will be a lot more confident going in that way, and with the massive ridiculous debt load I am already taking out, if an extra grand will give me any sort of boost (even just an internal one) then I think it might be worth it.