Looks like I may be the only person on here who can help you on this!
I took the PCAT in June '06, and I've been helping my boyfriend study for his DAT for the past few weeks.
Not to discourage you, but the DAT was significantly harder than the PCAT. Although I think the different versions of the DAT are of significantly differing difficulty (I think he got stuck with a harder one). From the postings online and his practice tests, it seemed he would be fine on the DAT (shooting for a 17+), and he got a 16, but he experienced much more difficult questions/material, he said, than were posted/indicated in some of the DAT forums.
I would consider my boyfriend and I of quite comparable knowledge and ability, and I pulled an all-nighter reviewing for the PCAT the night before the test, while he has been studying for a week and half solid for his DAT. As I said, he got a 16 and I got an 86th percentile.
The biology seems more in depth on the DAT, the math was definitely a little harder, there's more/harder o-chem on the DAT, and then there's perceptual ability (which you're pretty much either good at or you're not - he is, I'm not!). Then again, the PCAT has the writing section (I'm good at, he's not). You do, however, have more time per question on the DAT for math, which is a good thing (I haven't calculated for the other subjects).
Another thing that separates the two is computer vs. paper. I've heard from several people that the computer is difficult to look at for 4.5 hours: it has a flickering screen, very high resolution (meaning tiny font), and that people tend to wander in and out of the testing room (cleaning, fidgeting with the blinds, etc.). Also, any notes that you would want to make on the figures, in the math section for example, means that you have to redraw the figure when you're working on the computer.
Well, that's about all I have to say for now. I think what my boyfriend would recommend is to feel competent and ready for the test before going to take it. He took physics classes over the summer, leaving him only a week and half to study for the DAT before fall classes started. He committed to taking the test before school started, but when it got closer to time, he just didn't feel that he had prepared enough, and that really hurt him.
All I can say is I'm glad I didn't have to take the DAT (especially the perceptual ability)! But I wish you good luck on all your tests...study, study, study!