I had my first CX race today (Kiss Kross series) and did pretty well in the B's but a huge slowdown for me was the dismount especially. I have a really hard time doing the rolling leap that a lot of guys do. Also I carry on my left side since I prefer to hop on the bike from the right side. I can remount fairly cleanly but any tips here are appreciate also. Is there a huge disadvantage to carrying with the left other than potential snags from the drivetrain?
no real disadvantage... the chain will cover your jersey in muck but you should be fine. The only problem can be when other riders get in your way because most people dismount left, they may ride up on your right hand side as you go to get off but then, they'll steer clear of you if you knock them around so don't worry, just practice them as much as you can until you are smooth.