I have no experience with the BOB. I bought the Chariot Corsaire XL for the reason that it was the largest bike trailer on the market. It can take up to 100 pounds, and believe me, I've tested its limits! I had my 9 and 7 year old in there (they're skinny) and if you want a real workout, you can try that some time, on an incline! The Chariot was the main mode of transportation for our family, taking the kids to preschool or baby activities. It wasn't to help me exercise, it was to replace a car. But if you want some amazing power workouts, it's the way to go. I had a separate $150 Costco running stroller, which I never used for running. We sold it for $50 when we were done with it. It was our main stroller when we had one child. We also had a double stroller, $80, tandem style. Much easier to steer in tight spaces.

I suggest that it is actually better to use a treadmill and rollers because IMHO it is uber boring for the kids. Instead of having their heads bouncing around, I can let them play while I'm on the treadmill/trainer, and when I'm done, I can take them for a real walk where I can spend time talking to them, pointing out sights, etc. When sitting in the trailer as a mode of transportation, I supplied them with books, music, and lights to read.

I would not recommend sub-zero use only for the reason that it is hard to judge when the kids are freezing, even if you give them a blanket, because they're generating next to no heat because them are only sitting around while you sweat your face off.

The main problem with running too early is that my breasts were full of milk. Baywatch. And I'm an AA cup, and found that it was too uncomfortable to run with my jugs bouncing, full of milk. So I did not start running until my youngest was 2 years old!