Primary radar is still the best insurance policy an atco can get in an ATC radar environment.
Obviously Sweden has primary radar for its military. It would appear that they don’t share this with their ATC. But that (lack of sharing, and resulting radar duplication) is normal around Europe.
Swedish pilots just have to carry transponders if they want a radar service, which seems very reasonable to me… the UK should have such a rule too and then we wouldn’t get the ridiculous traffic reports like “aircraft at your 12 o’clock, closing, 1 mile, altitude unknown” 
What good is a primary radar return in a high traffic environment? Are the data blocks still attached to the echo, although without altitude and other data provided by the XPDR?
The radar is obviously unable to get these data on its own, but the controller can assign a tag to a radar blip, and it will stay with it for as long as the radar can discriminate this blip from other ones. It’s also possible to distinguish a helicopter from an aeroplane by the Doppler spectrum of its radar return, but I am not aware of any civilian radars that do it.
In the UK there is a rule that ATC are not allowed to vector a primary-only return, or something vaguely like that… I don’t recall what it was exactly. Clearly whatever it is, it doesn’t apply to Sweden.
It is as Aviathor and Peter says. Swedish ATC has secondary radar, but not primary radar. All primary radar stations were decommissioned some decade ago – as a cost saving measure, I guess. AFAIK a new primary radar station is being built for the Stockholm area, so our national ANSP must has realised that is a bad move.
Of course the air defense system has primary radar, but there is no feed to ATC. So when the Russian Air Force turns up over international waters in areas with dense traffic with their transponders off (which is happening more and more frequently), our air defense calls ATC and provides them with traffic information.
