I booked two trips through Nordic Visitor, and both of them were really nice, for the most part. One was the south coast + glacier lagoon and the other one was Landmannalaugar, with the bus.
1. When they send you the email confirmation of the booking with the vouchers, this is what it states: "Please notice that you must print out the vouchers and present them to the operator for each pick-up."
So I printed the voucher and presented to what I thought was the operator. I was picked up at a hotel, the driver didn't want my voucher, but didn't say anything else. Then, I was about to board my actual tour bus, and the tour guide refused to take my voucher and told me he needed a ticket. That's it, no helpful guidance, just that he needed a ticket. So I had to ask him where I would get a ticket, and I ended up having to walk back to the office to exchange it for an actual ticket. This made me lose first choice for seats and caused quite some annoyance during the 14hr+ trip :/ I know you can't choose your fellow passengers (kids who will not stop talking, seat mate overextending, sometimes into my face and keep accidentally touching me), but that's why I like to board first. Anyway. The girl in the office instead of apologizing for the confusion, stated to me that what I had was a voucher and not a ticket. No kiddin'. It would be super helpful if your emails would explain what the procedure is and / or the pickup drivers advise about this. Oh and a bit of courtesy goes a long way. There are plenty of other tour operators to choose from. This is likely not your fault entirely, as I had to deal with the company directly that *you* contracted.
2. When food is not included in the price, you're at the mercy of road side cafes and gas stations and you gotta order and eat quickly, especially when the 30 other people on the bus is trying to do the same thing, including use the restrooms... and 2 other tour busses just stopped by. Suggestion: pack your food and bring it with you. It stays cold enough on the bus.
It would be helpful is the tour companies listed some sort of idea of what to expect, ahead of time, but it's doable. You could also call ahead and get some details, and they may able to provide it for you.
3. No restrooms on the bus (at least not the ones I took). So yeah, keep that in mind. They are nice enough to list all the breaks that are coming up, so you can so some 'planning', hehe.
So yeah, all in all, good experience, the drivers were nice, and the programs were good.