Harder: Eyestrain. Monitors were ancient and not properly configured at my site. Also, I feel like you need to know the material better in order to nail it - 1 bad passage can rock you. Be on the look out for glitches.
Easier: Less fatigue. Make sure you bring a snack and take your full breaks.
Prep: I used pretty much only the ek subject books. I took the Kaplan and TPR free online diagnostics in CBT format. I did amcas 3r, 8, 9, 10, the latter three are cbt as well.