The time of year you want to visit is an important consideration for the trip. In summer you have lovely long nights - Midsummer celebrations. Stockholm is a must, as are the archipelago's off the coast. We have visited Gothenburg which we loved for the ease of public transportation, all of the natural beauty, museums, and the archipelago's off the coach. We also visited Kalmar and Växjö - in Smaland - known as the glass district and castles. And inland to some of the lakes and hikes.
It is a beautiful country if you like nature. Winter is different - it can be dark and damp. But the cities are beautifully lit and they have a wonderful Christmas feeling. In addition to the time of year, the amount of time you are visiting, and whether you want to travel by car or train/public transportation. Also, take into consideration the cost - it's not an inexpensive place to visit.
I was pleasantly surprised by the restaurants we ate at in Gothenburg, Stockholm and some of the smaller towns. Of course, there are traditional Swedish-style foods - open sandwiches, salads with shrimp and mayo, meatballs and salmon. But they have many delicious "foodie" food as well. We ate our way through the trip. We do like hiking and skiing and cold weather so for us it's a perfect balance with our interests.