Treadmill vs. running outside

In these cold winter months, it is really tough to convince myself to go for a run outside.

While I know that running outside is a better workout than running on a treadmill, some days when I don't get to my run until after 5pm and it is already dark outside, I will stick to an indoor workout.  I like going to the gym to lift weights, so while I'm there, I try to get in at least some sort of running/cardio.

On the treadmill, there are two ways I typically approach my running:

1. Intervals.  Using different speeds and different inclines, it keeps me interested in the workout (since I don't listen to music while I run).  I've been wanting to try this one for a while, but haven't gotten around to it yet: Print It Cardio: Treadmill Pyramid Intervals
2. Splitting my running time.  My last trip to the gym, I split my 2 mile run into two, 1 milers.  I walked for 5 minutes on the treadmill, then ran for a mile.  Did about a 40 minute lifting routine. Than ran another mile. 

p.s. I remember reading somewhere that if you're running/walking on a treadmill you should have it on at least a 1.0 incline to mimic the effects of running outdoors