My dd who is doing Bigger did not like the Colonial Science book at all. I have no idea why. Over the years I've done too much switching to accomodate the preferences of my kids, so on this one I decided to stand firm. It ended up being a character-growing opportunity for her to do her work well, and I'm very glad we stuck with it.
My oldest is doing Preparing science and she could really care less about dinosaurs. Same thing...I told her she really needed to do the work cheerfully and in a few weeks she would be onto a topic that interests her more. With her, though, she has ended up really enjoying the book!
Both girls have loved every other book they have used. I think the variety of Science books used in HOD is great, as it keeps things fresh and interesting
Our only real issue has been that ds (our 6 y.o. science nut) has been quite jealous of his sisters' science. We've added alot of science-related books and CDs for him while doing LHFHG, since this truly is his passion. He says he wants to grow up and be a "Vertebrate Paleontologist" 
(Jonathan Park fan will get this.)