Not sure how many of you use a "dreadmill" during the winter, but I started a few years ago and have had some great results. If anything, I get a run in when I might opt out because of many reasons outside.
Here is one I did yesterday. I like the fact that you can track progress and keep conditions static (except for the temperature inside the house). This is a hill workout I started in prep for Ice Age 50. I struggled before the race to complete 6 of these intervals, but was able to do 7 yesterday (and not die on the 7th).
Warm up with 1 mile at 8 minute pace, 2% incline (i always keep at least 2% to simulate actual road running).
Drop the speed to 6 miles per hour (10 min pace) and increase incline to 12% - do that for a half mile.
Recovery interval = reduce incline back to 2% for 1/4 mile.
The first couple of intervals seem easy, but they get tough.
This is almost like a combo workout; Hill; kind of a VO2, kind of a Lactate threshold.
Give it a try. Let me know what your hill work outs look like.