I've used DC++ in the past, its completely unique that's for sure. As the name implies you directly connect to the other person's harddrive and search through it, almost as if you hacked into his system. DC uses "slots", one for each member to connect, no availble slot means you have to wait. The good news is that usually you will have a faster connection to the file (how much faster I forget) and it is more reliable.
The bad news is that in order to gain access to many of the rooms (its similar to a listing of IRC chat rooms) you need to share an enormous amount of diskspace. Sometimes reaching over 100GB. All in all its a good system, and you should give it a try.