For my circumstances and my car they are necessary and make a huge difference.
I also think they are necessary for the girlfriends car - I need to know I've done everything I can to keep her safe whilst driving in the winter.
Everyone has to make a decision based on their unique circumstances - just don't f
ing moan about the lack of gritting etc. etc. when you get stuck or crash because you chose to drive in bad weather with unsuitable tyres.
I won't do another winter without them.