Yes the only function of this free voucher is to skip the queue at the security check. You can buy other things like porter services (i.e. what used to be know as Red Caps)
I used it in T1 on the Tuesday morning after Easter.
As it happened there wasn't a huge queue for the security check anyway but we rambled up to the express lane anyway.
I presented the Airport Genie vouchers to the women there and she first told me that no this lane was for business class or whatever.
But I insisted that the Airport Genie vouchers served the same purpose.
Jaysus, sorry luv, nobody has briefed me about these things was the reply.
So there then ensued about a 3 minute delay as she tried to figure out how to use them, consulting a colleague first and then calling over her supervisor before letting us through.
The vouchers have to be scanned in conjunction with the passengers boarding card and as there were 4 of us travelling in a family group this caused her some difficulty in trying to figure out which voucher should go with which boarding card
She didn't manage to get two of the vouchers to scan properly as the system kept saying "passengers boarding card must be scanned first" even though she had just scanned the correct boarding card.
So at the end of all the rig-ma-roll she called over the supervisor and he said to her well just visually check that the dates on the voucher correspond and let them through.
So in our case we probably would have been quicker in going through the normal channel.
Hopefully these teething problems have been ironed out by now but the need to scan the voucher in conjunction with the relevant boarding card is definitely a shortcoming of the system if you are travelling in a large group and one that could and hopefully has already been corrected by a little computer programming.
I realise that you probably don't need to know all these gorey details I am just posting them here in the faint hope that someone from Airport Genie would see them and take note so as to improve their system.
I was of course using a free voucher on that occasion, had I paid for it I would be demanding my money back.
Would I pay for the service in the future? No, not unless I knew the system had been vastly improved and even then only if I were travelling at peak times such as the end of July.