I took a two weekend Veritas course and got mixed results. My quant went up 4 points but my verbal, which was what I really needed to improved stayed exactly the same. My AWA did jump up however.
I think the quant is a lot easier to improve in a short amount of time. But once you learn their concepts on the verbal you really need to practive them for a while which is why I did'nt like the weekend course.
They let me take the full 13 week course for free on-line since I wasnt happy with my score increase. The problem I have is that here in Ohio the better prep courses (Veritas, Manhattan) don't have full in-class courses because there arent enough people who sign up.