I've used them a few times in the past m8 with no problems whatsoever.
Both Paypal and Nochex were on a par with each other a few years ago, until ebay bought paypal and it became the "default" auction payment method.
Nochex used to only accept debit cards, ie not credit cards so I suppose that may have held it back a bit.
I suspect that the fees are less for the vendor using Nochex too, that will be why he prefers it.
i have also used nochex with no problem at all,just make sure the other guy is legit. if you use it,it can take upto 3 days to set up because they check you who u say u are via ur bank details and u have to confirm by saying how much they took out of your account(between 1 p and 99p) mine was for 1p.if you wanna test it send me loads of money via my nochex account. hope that helps