A year ago next week my GF and I took an Icelandair package to Reykjavik for a long weekend: left Thursday evening, back Sunday. Despite hitting the worst winter weather the place has had in decades and too much cloud cover to see the Northern Lights, it was fantastic. Swimming in the Blue Lagoon, parts of which are too hot to stay in, while there's a 15 degree F blizzard going on around your head, must be experienced to be believed.
When we go back it will be in August, for longer.