I think their software is pretty good. I've done 2 out of the 5 tests so far, but I like it. Achiever is good too. Haven't used crack the oat.
For Chemistry and Physics, if you can get a hold of princeton review MCAT books that would do wonders. My weak areas are Chemistry and Physics as well. My boyfriend has a set of princeton review books and I studied from those books for a bit to try it out and realized it does a much better job explaining all of the concepts than Kaplan so now I'm using the princeton review books for concepts that are hard to understand.