Another ancillary factor in all of this is that speed matters. Results matter, particularly when you're obese. I was 290 lbs in mid-December. The ability to lose 65 of those pounds in three months has provided me with all kinds of momentum. My plan is considerably more restrictive right now than how most people do primal. But it doesn't feel restrictive when I'm losing 3 to 4 lbs a week. Yet, I could imagine finding giving up grain to be a lot more bothersome if I was only losing a pound a week. Maybe I'll feel differently if I plateau before I lose another 30 or 35 lbs. But so far, I haven't seen a reason to start slower. My metabolism has slowed just about as much as you would expect for having a body that is between 1/4 and 1/3 smaller (I use the bodymedia armband, because I know that even if it's inaccurate, it can show my current metabolism against my metabolism 45 days ago).
Tracking eliminates excuses and uncertainty. If you're truly limiting carbs and eating a significant caloric defecit and you're not losing weight, then we know we can look to other hormones to fix.