Before buying I did alot of research, and what little I could find was mostly about the old Nordfrost 3, and also more from Subie owners, not so much on Germans. Since there's so little info. out there about these tires, so I figured I'd share my thoughts. I'll post more as I have more time on them.
I got the Gislaved Nordfrost 5 in 225/45/17 a couple weeks ago and have been running them on the stock 17" Avus wheels. These things are awesome. Studdable, but not running studs. With the exception of very few regions, almost nobody needs studs with AWD and Winter tires. I've taken them up to the local ski resorts a couple times so far, and they've been great. They grip really well in packed snow and on ice. 0 slip when moving from a complete stop and you really feel them at work.
Obviously they have a soft tread compound, so dry pavement handling def leaves something to be desired. I can clearly feel the soft sidewalls when cornering hard. I wanted the best grip for snow/ice, which means a softer compound and softer sidewalls, so this was a tradeoff I was more than willing to make. I had a set of Dunlop Wintersport 3D tires on another car which was great on dry pavement, but at the expense of some grip on ice. I have no problem leaving the aggressive driving for when I throw on some 18's in the summer with lower pro high performance summer tires. **** all seasons. If you can only have 1 set, then whatever, but otherwise it's just a compromise in every category and doesn't excel in any of them.
Between my rack and these tires, fuel economy is definitely suffering, but I've only owned the car a month which isn't long enough to quantify the difference.
Gislaved isn't related the Nokkian, but since they're both Finnish companies, you can draw your own conclusions. Both the Nordfrost and Hakkapeliitta rate highly in their tests. The old Gislaved Nordfrost 3 was discontinued, but is now sold as the General Altimax Arctic. Both brands are owned by parent co. Continental. Supposedly that was a great tire as well, but I think it's safe to assume the newly redesigned version is better. Since I got the 5 for the same price as the now relabeled 3, it only made sense to go this route. Besides, the General is only speed rating Q (99mph), and I had ruled out all Q rated tires in my search. The new Gislaved is speed rating T (118mph), which I feel more comfortable with.