After doing some research and talking with people on Afib related forums, I've decided not to go through with the cardioversion. I don't have any symptoms other than an irregular heartbeat and one of the possible outcomes is that my heart rate may change for the worse (become too slow or too fast) after the cardioversion. I'd rather keep things as they are and continue to monitor the situation. If my ejection fraction gets worse, or there is significant dilation of the atria, or I start having symptoms I'll reconsider my options.