The mild winter might be good for people's wallets, but is not good for nature - it messes up the growth and flowering rythem of the plants, takes the pollinating insects out of sync with the flowers, and in general increases the amount of pests.
Also while its a bit milder than normal at this time of the year, its still freezing! Was sat working in my unheated house earlier, and then needed an hour to get halfway warm again. I'd rather have proper winter, or proper warm weather.