Do it. It's worth taking if nothing else just to get used to the testing format. The KAPLAN book is garbage though. I found the real PCAT questions to be a lot easier (especially verbal) and the reviews are dreadfully boring (you won't want to study them).
The biggest help for me was not going over mass amounts of info, but getting better at deducing correct answers and creating strategies like simply reading the Q's first then the paragraphs in the reading section.
fyi, It's PCAT, not PCAT'(S) and there is a PCAT FORUM aside from PRE-PHARM where this thread will ultimately get bumped.
I bombed the official PCAT practice tests, but made the real one my beetch.