I have an iPhone with "Telia Sonera". It's mainly because I'm not able to choose due to it's a company phone.
My father on the other hand has a contact with the provider "Tre" (also called "3" or "Three" if you wish ).
Telia is often considered as "good enough", it's the biggest provider in the country with good all around coverage. But they sometimes lacks in speedy coverage and they can be a bit more expensive depending on the kind of usage.
Tre (3) is a 3G-only provider. They also has good coverage. Tre is having, what I know about, the fastest data speed and okay prices.
Telenor is another provider that bought Vodafone's infrastructure here and I haven't had to good experience with them, they have strange price models and worse coverage than the rest.
Then there's Tele2. They often have quite nice packages for "young peoples" with good call-your-friends-with-the-same-provider deals and sms packages. Their coverage is OK and but they usually have more expensive data plans. I don't have to much of experience with them though.
I would recommend to go with Tre. They have good coverage, fast data network and OK prices.
Other Swedish people are free to bash my comments!
Thanks for your input. I can't believe reception is equal amongst all providers, it's not even that in UK. But thanks Bolen, I will pass on your experience of your countrie's providers to my neice. She's looking forward to her time in Sweden, but as she's coming from Los Angeles I'm warning her to prepare for a different kind of 'cold'.
Tack för dina synpunkter. Jag kan inte tro mottagning är lika hos alla leverantörer, är det inte ens det i Storbritannien. Men tack Bolen, Jag kommer att framföra din upplevelse av din Countrie är leverantörer till min systerdotter. Hon ser fram emot sin tid i Sverige, men eftersom hon kommer från Los Angeles Jag varnade henne att förbereda sig för ett annat slags "kallt".
Cellphone reception is almost equal because most of the celltowers are owned by TDC which allows the rest to "borrow" their network. Rather their forced because of monopoly issues.
Three owns their own 3G-only Network and that's why they have the best 3G coverage.
offtopic: why would anyone move from southern cali to friggin sweden?
Stay away from Tele2 and Telenor, Telenor owns Tele2 and the company is constantly buying up smaller companies and trying to grow, I have had bad experience with them and and the service is bad.