I wanted know if the trip to Gotland is recommended considering the time it takes to get there. I do not want to fly but take ferry. We will not be rushed and could easily stay a night or two. Can you share your experiences and thoughts. We will be coming from Stockholm and going to Copenhagen after.
I can't answer your question but just wanted to make a comment. We tried 2 times (July of each year) to go by ferry to Gotland. Each year a large convention was being held and the visitor office indicated there were no hotels available. Not sure when you're thinking of going. I hear it's wonderful.
Gotland is a beautiful island and Visby, a wonderful old Hanseatic city. I'd recommend spending at least 2 nights, which will give you a day and a half in Visby if you take an early ferry. You can take a train from Stockholm to Nynäshamn (about 1 hour, trains every 30 min.). There are up to 6 ferries per day in summer between Nynäshamn and Visby (about 3 hours). See this website for ferry schedules and prices: www.destinationgotland.se. (fares vary depending on day of week and how far in advance you book).
If you are heading to Copenhagen after Visby, you can take a ferry from Visby to Oskarshamn (3-4 hours, 1 or 2 boats daily in summer, see above website for schedule). Trains from Oskarshamn to Copenhagen take about 5 hours with a train change in Nässjö.
If traveling in the summer, I'd recommend booking the ferry tickets and hotel ahead.
I really like Gotland and was always surprised that it wasn't in the RS book (although perhaps things have changed). I visited round trip from Stockholm and did as previous poster noted taking the local train (pendeltåg) to Nynäshamn. The town of Visby has the medieval wall and church ruins. I rented a bike one day and rode out to Tofta Beach one day which is a nice sandy beach.
As Sharon mentioned, you need to book in advance if you are visiting in summer. There is always some sort of political convention in July and a medieval week in August. I visited in early September when tourist season had passed.