My wife and I had a great time camping in Iceland using our Campervan Iceland (www.campervaniceland.com) this summer! We travelled around the country in 10 days and we loved every minute of it. The guys at Campervan Iceland were very helpful so we would definitely recommend them. They're friendly and very willing to give tips and help you plan your trip if you want.
I did notice how a lot of things are more expensive compared to the US, but that was to be expected. But we definitely liked the pickup and drop off service that's included, it really helped after a really long trip from the States.
The camper van had everything we needed and we really enjoyed not having to worry about finding hotels/campsites every night and just be as spontaneous as we wanted. We most definitely will be back to Iceland someday and I think we would get a Campervan Iceland again.