Spleen United have been around for a while but I only discovered them a few months ago. I'm assuming that they're huge in their native Denmark as their album Neanderthal, released back in January, quickly earned gold record status in their home country and the first two singles ('My Tribe' and 'Suburbia') have been getting tons of airplay. The band has been selling out Scandinavian venues all year and recently ripped it up at the Roskilde Festival this summer.
I haven't listened to the whole album, but I do like the tracks I've heard so far. Comparisons to Muse and The Killers make sense, and these guys actually do synthpop without coming across as lame.