I'm currently a direct entry MChem student at St Andrews. I did OCR chemistry and got an A*. The textbook was fantastic and I really liked the layout of the course. However, since starting University this year (directly into second year because it's Scotland etc) I have come to change my mind a bit. There was a huge jump from A level to university teaching and while this may be because university level content is harder, and because I went straight into the deep end with direct entry, I still feel like I was at a slight disadvantage to my other direct entrant peers. The majority of them did Edexcel or CCEA and were taught at A level several of the 'basic' things that I struggled with during my first semester. This obviously made things very hard for me as I was spending a lot of time trying to learn things on my own that everyone else had been previously taught instead of focussing on the completely new content.
Personally, if you are considering doing chemistry at a higher level, I'd recommend not doing OCR (or just not being an idiot and deciding to do direct entry) and doing Edexcel instead. If you are planning on quitting Chemistry after A/AS-level then OCR was a great board and I really did enjoy the course. Hope this helps!