We had a very nice weekend in Stockholm, in between two planes, with two nights at Hotell Kristina. The breakfast there is really excellent (I think hotels in Sweden have generally a better breakfast than in the rest of Europe, actually). The free wifi and the pool table are nice additions.
The only downside is that it takes 1 hour by public transportation (bus+train) to get to Stockholm Central (train station). Only 30 minutes to the airport though, so this is a better airport hotel than tourist hotel. Unless you're fine with 1 hour of transportation of course :)
We don't regret it, Sigtuna is much nicer than any huge city downtown.
Another small downside: no way to roll our suitcases up to the hotel, with all that gravel outside, and stairs. I wonder how people in wheel chairs can go to such hotels...