I really wanted to read Kaplan but had not enough time. I enjoy biochemistry and I think that Goljan's book is great for learning the basics and doing well on practice NBME and on QBANK. It is a time committment compared to high yield or first aid, but I was biochem naive when I began my studies.
THAT SAID, biochemistry proved to be the lowest yield subject on my exam and I am a bit disappointed because I prepared heavily for it. The questions I received were straight forward and picky, but pertained to some of the "lower yield" pathways and mechanisms of which I knew very little (so yeah, it panned out as satire... let's all point and laugh at me!). There was nothing on the exam that was not in Goljan, but it was not as fresh in memory as the "high yield" pathways that I spent more time on. There may have been a few things that were not in first aid. Are you gonna remember Goljan? Do you have a broad biochem background? Is it going to matter if you only receive ten biochemistry questions? Depending on how you answer those questions, you may want to supplement with Goljan or you may way to stick with first aid.
No matter what, read first aid. Seriously. It has give-mes all over the place.
Everyone told me to pay more attention to cell and molecular biology and I am glad that I did. I am spreading the gospel of HY Cell/Molec. Big Frank mentioned how it helped him get a 317 (or whatever he got) and I took his advice and read it. My exam was loaded with stuff from that book. Then again, that was just my experience.