I use Freecycle all the time, and love it. There are great people that use it, and also some really greedy creeps.
One thing to remember is that you get to decide who you give your items to. If you don't like the sound of someone, just say the items are spoken for, or you can ignore them. You don't have to give them to the first person to reply, or to the pushiest person, you can chose to give them to whichever responder you like the sound of.
My favourite weirdo was a woman that got terribly upset at me and threatened to call the cops because I gave away a VCR to another member instead of her. I told her to go ahead
One thing I have learned to do, is to add a line or two on each offering or each private reply stating that certain conditions apply, such as a time limit for responses, a no show policy, limited quantities etc... Once I had about 50 old computer games and I didn't want a dealer taking them and reselling them - I wanted people to play them. So I put a limit of 5 games per person. Another time I had a broken computer that was really only good for a dealer to strip and reuse the good bits, so I indicated that it was best for dealers or people that could repair it. Some people gave me a hard time about these restrictions, but I ignored them (why do some people think being rude to me will make me give them something ?!?).
In general, I ignore people that are not polite in their initial contact, or people that give me odd vibes. But my Freecycle group has 12 000 members, so there are always a ton of people replying to any post and so it's easy to find someone I like the sound of
BP