This question seems to asked about the same time every year, there was a thread last year on CB.com. A soft top is doable through the winter here, even with a original heater setup, but you'll need to dress for a drafty vehicle and throw a blanket in the back for any passengers. I have a hardtop for mine that I've never put on yet (came w/the purchase), but I keep it just in case the crazy
grabs me to put it back on. I ran a soft top all last winter and commuted to work a few days a week and did some 100 mile trips without a problem and the only problem I've had is a cold shoulder from the draft at the door jam.
Warmth in an issue with soft tops in the winter of course but so is road noise, draft and condensation, not to mention security. Condensation is the big nasty with soft tops...think about a rain or freezing rain followed by a solid freeze. It will snow inside your car as soon as you break 10mhp! Take it from a guy who rocked a soft top and soft doors on a CJ year round in Michigan.