The biggest surprise is how informed today's first-time homebuyer is. They do their research, and to my delight, are not as wary of Real Estate Brokers because when I give them professional advice, they know I'm not feeding them a line, and the mutual trust and respect make the process smoother for everybody.
I didn't really answer the question, so....the biggest surprise a first-time homebuyer encounters is usually how much home they can actually buy. Some buyers overestimate how much home they can afford, and some are surprised to learn that they can afford much more than they initially thought. Before you go shopping for homes, even from your home computer, talk to a Mortgage Professional. Better yet, talk to three of them :)