Last Summer (08) my son and I rode the CDR. We started at the North end and travelled South. We had two weeks of time available and that included driving out from St. Paul, MN. So in reality we only had about 10 days on the trail.
We only travelled on the trail from Canada to Pinedale WY. which is about half of the total distance of the CDR. That probably seems like we didn't get very far. And that is true compared with other riders I've talked with. While we were on the trail we drove slow, soaked up all the beauty we could, stopped often, took hundreds of pictures and in general had a very relaxing and enjoyable time.
From my perspective, trying to do entire CDR in two weeks means that you'll need to be travelling pretty fast and not stopping very often. I'm sure it is a wonderful trip either way.
Because we took about 500 pictures I have been able to re-live that trip numerous times over this past long, cold winter.
Good luck on your trip.