We always use Mears. They charge $19.00 round trip/person. You can either pick up the vouchers at the Mears desk in the airport when you first arrive in Orlando or wait and call the day before you want to go to Universal. The Mears desk is right next to the DME desk. If you do get the vouchers beforehand at the airport, you can pay cash or use a credit card. The vouchers only have the date you purchased them on them, not a pick up date, so they can be used any day. Just call Mears the day before you want to go to Universal and arrange a pick up time. When the van driver arrives give him your voucher, he'll tear off 1/3 and give you 2/3's. About an hour before you're ready to leave Universal give Mears a call to arrange a pick up time. Give the driver the voucher again and he'll tear off another 1/3 and give you the final 1/3 for your receipt. The $19.00 does not include gratuity of course.
If you don't want to get the vouchers at the airport, you can just call Mears the day before you want to go to Universal and arrange a pick up time. When the driver arrives you'll have to give him exact cash though. He will not be able to take a credit card. You will not have a voucher. The process is the same though. About an hour before you're ready to leave Universal, give Mears another call for a pick up time. The Mears number is: 407-423-5566.
We've used them several times and have never had a problem. They may make a stop or two at another resort, but if they do, it just takes a few minutes. We've always arrived at Univeral well before opening.
This past May a friend joined us. My husband and I had prepurchased the vouchers at the airport, but our friend did not. When the van arrived at POFQ my husband and I gave the driver our vouchers and our friend explained she didn't have a voucher and just gave him cash. She didn't have a problem. He just gave her a voucher to use for her return trip that evening. Ours was the yellow cardboard type whereas hers was just a white paper receipt thingy. When we were there in Oct we used them two different days. My husband and I had prepurchased four vouchers at the airport again so used those both days. We noticed others getting on the van and some had the vouchers from the airport and some just paid cash. None of the drivers had a problem taking either. Now you do have to call ahead of time to schedule a pick up time. When we used them in Oct, there was a family that came running up asking if the van was going to Universal and the driver said yes and asked what time their pick up time was, as he already had the number he was supposed to pick up at that time. They said they didn't arrange a pickup time, but wanted to go to Universal that day and thought they could just catch any Mears van. He gave them the Mears number and told them they had to schedule a pick up time, in order to get on any of the vans.