I'm yet to take the DAT this year, so keep that in mind.
Took a Kaplan course and felt that it was too broad. It is good if you use it for an outline, but Bio is handled a lot better with Cliff's Bio (though there are some things missing that KBB does cover); GC and OC are far better taught through Chad's and Destroyer. Kaplan has a decent section on QR, but again Chad's is way better.
Kaplan is useful only if you need more practice questions than QVault, Destroyer, Chad's, Achiever, and CDP; and if you are making zero progress studying alone and need a structured syllabus to motivate you. Otherwise, it's really just an outline and your $ can be far better invested elsewhere.
If you've already bough Kaplan, use their practice tests and workshops to quiz yourself. That is, read the KBB chapter quickly to get an overview. Then go to a more detailed source - Chad's or Cliff's - on the topic and take notes from there. Do the practice questions and go over anything you missed.
Ultimately, practice, repetition, and perseverance will be the deciding factor in how your studies go.