As purplemania said, it does depend on your learning style and test-taking style. I think taking Kaplan can't hurt you except financially. So if you can afford it, I'd say go for it. I know it has helped several of my friends pass who just needed the confidence and extra edge to go in there and pass.
Other friends of mine who took it and didn't pass with it, had difficulty with more content and knowledge-based questions. Kaplan teaches you how to pick apart the questions and see through to the answer. So expect to do TONS of questions.
The best part of Kaplan in my experience is the book and CDROM. If you can get 60% or higher on those tests, it is a good indicator you will pass. They are very similar in style and even the appearance of the NCLEX.
Good luck in making a decision and we'll pray for your success!