I'm in a two-year ASN program, and just completed my first semester of Med/Surg. I thought it was very difficult - I got a B in it, and I'm usually an 'A student.' It wasn't as bad as some people say it is, though. We mostly learned about diseases (not treatments) of the different body systems. Some were pretty easy, I thought (digestive, respiratory) and others were REALLY tricky (acid/base imbalances). I have Med/Surg II next semester, which focuses more on treatments for different disorders. It's supposed to be much harder, so I hope I don't struggle too much.
One thing that I thought was really helpful for studying for exams this semester was making charts for every body system that we studied. For each disorder I would list the patho, signs and symptoms, etiology, diagnostic tests, and any other notes I could think of.