The food was good, but not great. So if you expect a "foodie" type memorable experience, you will be disappointed. However, it is a great place to try new things like whale, puffin, and sheep done up 600,000 ways.
Everything here is expensive. Every little damn thing. Expensive.
Go to the Blue Lagoon, even though it is the most expensive, most touristy place. It is a fun experience. But then use the local pools and baths.
The single best piece of advice we got was to buy our wine (or beverage of choice) in the duty free shop, for arriving passengers, down by the luggage pick-up. Don't get sidetracked up by the gates. It is down by luggage. In towns, we had trouble even finding wine stores, and they were never open. A little mini bottle of crappy Spanish wine will set you back $11 at any restaurant. Really.
If you are just coming to Iceland then going home, bring lots of warm stuff, even in summer. The locals can eat outside in shorts and a T-shirt when it is 8 degrees C. Not me! Iceland is not the "sit outside at the cafe" kind of Europe. At least it wasn't for us, this year.
Three days in Reykjavik was enough. On a second trip we would head right out of town, going north, and start our trip somewhere else.
It is hard to get a lot of sleep when it is light for 24 hours. I was always up past midnight, and would be awake at two or three; though I went back to sleep I was always up by five. I think fall or spring would probably be best. They say it is drier, and there would be dark nights and possible northern lights.
The people were friendly, and very hearty. The landscape is wild and beautiful. If you like the outdoors, Iceland is a Niceland to visit.
Perhaps, if Iceland wins the global warming lottery, the clouds will part, the temperature rise, and the winters mellow out. Can you imagine Iceland taking over for Hawaii? A verdant island paradise, miles of beach, natural hot springs, twenty-four hour beach days in the summer, and the northern lights on a winter beach night.