I've found it more useful for getting rid of junk rather than getting stuff, although I have had a few bits.
The idea really is about keeping things out of landfill rather than freeloading, so be wary anyone who's thinking about joining up to fill your boots!
The communities can be pretty close and it's all about giving and taking.
My local group insists that your first post must be an 'OFFER' not a 'WANTED' and if you do request it should never be too specific, like Keslo66 asking for a pram/pushchair rather than a 'Mama's and Papa's Pliko Pramette in red, excellent condition please'
But play by the rules and you can shift/get some great stuff! I asked for Enid Blyton books and received a binbag of about 40! I loved them as a kid and wanted to read them to Stanley.
The only other thing is when you're offering something you can get innundated with replies. Rather than give to the first (which isn't fair as some needy people might not be at the computer) I give it 24 hours at least. After that, you can pull from a hat or check out their profiles to see if they're a constant 'taker' or dealer. I have the same people ask for EVERYTHING I offer but after I've given them something I try to vary it next time.