I was not familiar with Norrona (Norwegian company), however these have become one of my favorite pieces. This is very high quality construction, and is a mid to heavier-weight piece. The side zips are a masterstroke. When using as a mid-layer insulation for climbing you can simply un-zip the sides and remove them in about 20 seconds without removing your boots or shell. I also wear these as an outer layer for running on cold days as well as to the gym - where I zip them off to workout, zip them back on when I leave, no shoe removal required.
These are not good for skiing due to the full length, but Norrona also makes a Polartec 3/4 length zip on/off (called lyngen 3/4 Powerstretch, which I also now have) that is a terrific mid-weight for skiing.
Fit: Norwegians must be small people because these definitely fit small. I'm 5'8", 167 lbs, 32" waist, 22.5" quads, 15" calves, 32" inseam. The medium was too small (like skin tight). But the large fits perfectly. I can wear the large over a base layer, or just over underwear or gym wear. The fit is athletic, but loose enough (and the material thick enough) that you can wear these around in public without worrying about your naughty bits bulging out and frightening random strangers.
Bottom line is that Norrona has become my new favorite manufacturer for base & mid-layer insulation items. Both these and the 3/4 length pants I have from Norrona are spot on quality and function.