Caveat: I'm not a doctor, blah, blah, blah

My opinion is that warm before is fine (I tried it and it made me feel lethargic for a while, so i did not like it).  BUT you still must have a warm-up phase before running... you may shorten the warm-up, but my take is that a warm-up phase does much more than warm you up.  It may also help with gently compressing tissue such as cartilage, bringing your cardiovascular system up to speed, opening your lungs for more oxygen absorption, etc. 

Hot after a run is bad (assuming it's a vigorous exercise) because your cartilige, tendons and muscles (and maybe more) will be stressed and inflamed.  I know chiropractor said moist heat for your inflamed muscles, but I believe cold to be better directly after it happens.  Maybe warm is OK after many hours or a day or so, but cold helps reduce inflamation.  Heat will tend to attract even more blood to the area, possibly causing further tissue damage. 

Mark

Yes, I actually was relaxed and wanted to go to bed.  I thought it would motivate me on that cold morning, but I'm not even tempted to do that now. 

Mark

I actually tried "warming up" in a hot shower before a run earlier this year. It was on a business trip back East and about 35 deg outside, which is relatively cold by my LA standards. I found that the hot shower made the outside temperature feel much colder by comparison, and I was shivering for a good part of the run. I wouldn't recommend it.