Winter training

In this cold days, the want to train seems to be harder, for me, to gain. The snow falls, the cold, the night fall early in the noon, i always thought that winter is the badest season to run. However, many of track athletes in Europe seems to considered that it's a crucial period to get a right and solid build up. It's may be true for track athletes who will have to work specific speed just after the begun of spring, and naturally for the fews who are pure cross-country specialists. When i was more a marathoner i thought it was also a good way to build some Vo2max during winter to get some speed for the end of the road racing preparation. But now, where my goals are more endurance races, trail runs who will be more held in Summer? I ask myself sometimes about the efficiency of a serious training in winter, when i am less motivated to get out.
I recently read an article about the training in winter of Scott Jurek, and also about the cut off of most kenyans marathoners during that period: view scott's blog:
http://www.scottjurek.com/blog/
Interesting... may be I will try it next year. For the moment the days seems to get warmer and longer, the season will start soon, so i have now again the will to run!