Private limo from Paris airport to Center of city?

The easiest most reliable way to get from the airport into the city is a taxi parisien -- obtained by lining up in the taxi queue. A taxi is private transport. Shuttles and car services have the reputation of unreliability in Paris -- I'd never take one TO the airport where the stakes are so high. If their driver doesn't show that day or your plane is late or they just 'forget' they will keep your money and you will be stuck.

Janet has pointed this out before, and Brenda confirms it--that private limos from CDG sometimes/often don't work and disrupt your travel plans just when you're at your most exhausted.
It's an interesting detail about travel to some European countries. Based on customer service concepts here, you would think: if I reserve a private limo from CDG to the city, they will be there with my name on a card, waiting. Not necessarily so in Paris. Better to know before you go, rather than being blind-sided by cultural differences that could disrupt your travel plans.

Official Paris taxi's work really well. Get one from the rank at the airport, do not go with or talk to anyone who is out of their car looking for passengers.

I have used a shared shuttle and a private limo from CDG (on different trips). The pickup at the airport was a nightmare.
The shared shuttle was 2:45 late (after I called them to see why they weren't there) and the private limo more than an hour late.

Each of these companies did fine picking me up from the hotel for the return trip. However, I plan to take the RER this time from the airport.
Fortunately, I travel lightly with only a carryon roller and a briefcase that rides on top.

New post in forum today about easy bus service between CDG and central Paris. Less expensive than RER and perhaps a little more user friendly. This service starts in May.