I looked at these schemes in the past - always considered it to be too much an expense for the number of times I am asked do I take a card (about 6 times a year).
OK the frequency will increase as time goes nearer to when cheques will be stopped, but cash is a very good choice still, and I can always fall back on paypal.
OK with the latter they may say they will pay by PAYPAL later and then forget :
but I will have to have some added clause in terms of payment so if they do have a memory lapse then they may have to pay for it - a bit like adding £ to the bill which can be deducted if one pays within say 7 days. (we talking domestic here).
And of course, more then PAYPAL will be in the game as time goes on so their rates will get competative no doubt.