I agree that I wouldn't go crazy about it, especially 1st year, for pretty much all the reasons already stated. The RISE is mostly like the old questions. The better question is what people think is good for studying for the boards -- if you do that, you'll be OK with the RISE.
The answer to -that- is to study regularly and early, focusing primarily on what you're doing in your rotations at that time (like you never heard that before..). Sometime between 2nd-3rd year (out of 4) I'd start going back and looking at things you're not as groovy with. For AP, any of the good 2-volume surg path books is what, I think, you should spend a lot of time with early. I also got some good use out of the "Differential Diagnosis" book, because it's useful in helping mentally categorize and narrow your options. I'd say a separate cytology book is useful too, when you get to that point; I found DeMay's smaller book useful. For CP I think it's more of a mixed bag; Henry's has a lot of info on all things CP, but many of the sections are not a good read. And don't neglect Robbins! I had some attendings at one institution who scoffed that no path resident should BE a path resident unless they already knew Robbins, so don't bother reading it, it's too simple. At another institution I had attendings who used it as their 1st reference for everything. Either way, use it, read it, know it.
Ultimately the best book(s) are the ones you'll actually read and remember something from. Don't get caught up in getting the biggest book from the most famous author -- those can be good for reference, but not always good to read and remember useful pearls from.
For final year review, I thought Lefkowitch's AP Review book was pretty good, and for CP the "old" Mais' clinical compendium I thought was pretty good (the newer one just didn't read very well for me). One of the review courses is probably worthwhile to do (Osler, ASCP, AFIP, etc.). I also think it's useful to look over board-review type questions just to mentally get in the groove, though not so much to "study" per se.