FWIW, I read them in the German translation since I can't read Swedish either, and was told by those who can all three languages and compared the translations that it's better and closer to the original than the English translation. So I can't comment on the latter, but the German translation at least didn't have any obvious uh-this-doesn't-feel-right moments on the lingual level.
BTW, another thing: I discovered a while after reading the book that Stockholm (Edit: WTF
, I wrote Helsinki here originally for whatever reason) actually has fantastic Google Street View coverage (which came as a bit of a surprise, because at the time - two years back, I think - Street View was still just starting out in continental Europe), and it was fun to look up the places used in the text there. This is more true of the latter two books which are increasingly set there, though. In particular there's a chase sequence where characters cross from "lower <streetname>" to "upper <streetname>" that's a bit hard to understand the geography of until you look at the street and discover that its two lanes are in fact separated by an acclivity with stairs set into it at intervals.