I spent a month in sweden a couple years ago, and it was beautiful! I was staying in a small town outside of Goteburg. It was really nice, everybody was beautiful, but it wasn't that cold (I was there during July). If you can, try to get to some islands on the westcoast, they are so beautiful and warm in the summer. We were swimming in the 20 degree water! Just watch out for jellyfish and lighting storms! Those islands are so cool, because they are just covered with little summer houses, but there are no roads, everyone takes a ferry or boat to get there, and they either walk or cycle around the island. If you are in Goteburg make sure to go to the Liseberg amusement park and pay a visit to the HangOver rollercoaster! Stockholm is also nice, although it was a little rainy when I was there. But worth checking out. I was there on an exchange and staying with a family, and wasn't really old enough to go to/appreciate a bar or pub, but I'm sure there are lots of nice places around.
I'm going to be in Sweden as well at the end of July/Early August, and will be going back to Goteburg, stopping to visit friends in Lund as well! Should be nice!