I have played against the space wolves, and found them fairly simple to beat. However, I think thats due to the guy using them not been the best player in the world.
He had 2 15 man strong squads of bloodclaws (the CC ones, I think thats them) and tried to take out my 2 squads of wyches in CC. Needless to say he didnt win either assault. His other thing that worries me was the long fangs, as I saw him use them very effectivly the day before against my friends tyranid army. However, he deployed them further forward than I expected, and in the first turn I managed to take out all 5 with my ravager.
He did have a run priest as his commander, and that was one nasty part. It took out my ravager fairly easily on turn 2.
One thing I found amusing, he has that special character, the guy on the big wolf. In the second game I played against him, he charged my HQ unit (archon, Drazhar and 4 incubi) single handedly. And seemed genuinly shocked when I destroyed him before he got a hit off, haha.