I have participated in two swaps. One being the One Block/Month Swap where I corresponded with some lovely ladies from the U.S. and other countries and was very happy with the commitment and quality of the blocks I received.
The other was a Signature block swap with 174 participants and I was very happy with the organisation and result.
In both cases the quality of fabric and level of experience varied but you are aware of this before joining as these swaps were open to "all levels" so it is your decision whether go ahead and become involved.
I do think people need to read the WHOLE THREAD AND INSTRUCTIONS before committing themselves so they are confident that they can fulfil the criteria for the swap.
Having made the decision to join, jump in with a good attitude and enjoy making some new friends and have fun.