The easiest and least expensive way I found to get from CDG right to your hotel door is a shuttle service called Bee-Shuttle. It cost me 14.50 euros per person (there were two of us) to have a driver meet us at the terminal and drive us in a private, air-conditioned minivan, right to our hotel door.
I wanted to take the RER, but after a 9 1/2-hour flight with luggage and stairs, having to transfer trains at Chatelet and drag my bags from the metro station to the hotel... this was much easier and only slighly more expensive.
Thought about the Air France shuttle, but then again, we would have had to take a train to our final destination and deal with stairs and carrying luggage to the hotel.
You can arrange travel via the Internet at www.bee-shuttle.com. They operate from 5am to 11pm 7 days a week. I was more than pleased with the service and the price. In my opinion, it can't be beat.
The RER is a great way to get there IF you don't have a lot of stuff to drag around. For a 2-week trip, we had a lot of stuff, so this was much easier.
**** NEWS FLASH! ****
I have just returned from Paris again, and had absolutely no problems with Bee Shuttle. I had two friends of mine go to Paris 2 weeks apart and never got service from them.
The first friend called the number on the email she recieved from them, as instructed and was told she didn't have a reservation...even though she had a reservation number.
The second friend, 2 weeks later, called and was told the van was there. Nothin'. Called a second time and was told it would be there shortly. Nothin'. A third call, and 2 hours later, nothin'. He took a cab and paid almost 70 euros. Again, I never had any problems in the past--perhaps my friends weren't paying attention.
After you exit the terminal, all the respective taxi and shuttles are lined up, backed-in. Bee Shuttle was easy to spot and I never had to wait. I reccommend it for an easy way to get to your hotel, especially if you've never been to Paris before--it's much easier than trying to figure out the RER or pay an arm and a leg for a cab.