Ah, one of the greatest mysteries in life. Some say that it's their own fault partly for not being better known outside of Scandinavia.
You're right though, they have improved, kent (debut) was very mediocre, Verkligen was a bit better, with Isola it picked up, Hagnesta Hill was amazing, Vapen Och Ammunition was unique and good although I wish that Hur Jag Flick... and Duett were a bit shorter and they didn't mess Elite up by putting that stupid gospel singing in it, Du Och Jag Doden was a really strong album, some really hit songs on that, and Tillbaka Till Samtiden is really cool. Maybe it is their best work, who knows, it just lacks stand out tracks but other than that, it doesn't have any weak points. I even like Somnen now, it's sort of a bridge to the rest of the album and I've gotten used to the drumming in the last song.
Btw, you can buy their album for like $1 - 2.50 US from some sites like that site GoMusic.ru or some more updated one but it's nicer to get the actual physical album obviously. By the way, has anyone in North America had the album arrive yet? I'm still waiting.