That really all depends on what your needs are. Some people only need simple refreshers and some general tips on standardized tests. If that's the case for you, then Kaplan might be all you need.
My case: I benefited very little from Kaplan. The Kaplan program did not address my deficiencies nor provide me with adequate feedback to come up with a study plan. Two friends of mine took the Kaplan classroom program, one scored a 700 and the other scored a 750.
Knowing what I know now, I could have self studied. To solidify myself, I opted for the
MGMAT program.
Have you gone through the threads for beginners and/or taken a diagnostic test to assess where you are?