I have used the CO certs in NW clubs with no problem. (less than a year ago)

Create separate reservations for both of you on CO.com.
Then call CO.com tech support, have them pick up your companion record
and adjust it to the $99 companion ticket (rebooked in Q I think).
Both tickets can then be paid for with whatever cc or means you decide.
You can then send in the Prestige Pack voucher, or take it to your airport
so the ticket will be finalized and you are done.

FYI - CO.com said you will get 2 1,000 bonus miles if you booked the reservations separately, separate PNR numbers and EQM miles at 100% since they are .com reservations - fully mileage on the $99 companion ticket as well.

Both of you - see above.

I used the 99$ companion voucher to buy a ticket. The CSR told me to make a photocopy and mail it in. I made the photocopy and mailed it in. The reservation on the website never indicated that it was received and a week before the flight I called them. CO said they never received the voucher, and because I didn't send the voucher certified, there was nothing they could do about it. One CSR said to wait until the day of the trip because the voucher may make it in -- yeah, right. Another CSR said that I could pay the going rate at the time of the original reservation. I canceled the reservation and used miles to book the trip.

I have exactly the same experience. Apparently mail handling at Smith St is a mess. I even knew in advance I should send it certified to avoid this, but was too lazy. Trying to resolve the issue online also led to an unannounced phone ticketing fee (which I am considering disputing because it wasn't declared.)

CO is considering replacing the certificate but haven't yet got back to me with a decision.

What are the terms on this certificate? Does it work in Europe? Does it work on ANY rate?

did you read the thread? check out post #12.

For future reference, the threshold amounts for the discount certificate ($175-$274 -> $25 off, $275 - $399 -> $50 off, $400+ -> $100 off, who knows what happens if it costs $274.50? :) ) apply to the all-in price of the ticket, not the pre-tax price initially quoted on the CO website these days. So it's the more generous of the two possible interpretations.

Do any non-US residents purchase and successfully use the privilege pack? Are there any potential problems in using the vouchers on their local CO.com sites?

A onepass agent initially said I couldn't buy one as I didn't live in the US. After some discussion she said she could sell me one if I had a US address to have it mailed to (this wouldn't be a problem for me)- a poster, early in this thread said something similar.

Any comments would be appreciated. Thanks

So, by extension, would I be able to use these lounge passes in the KLM lounges in AMS?

You could try but I wouldn't raise my expectations, since even the WC access isn't a published benefit.

Does anyone know how I can use the certificates (OPCR and PPDD) online now that Continental has eliminated the hold feature? I can't start the reservation online without completing the purchase. I've been told my a customer service rep that once the purchase is completed (i.e., credit card charged), it is not possible to apply the certificate. All I can do is cancel (within 24 hours); and then book the reservation over the telephone. Of course, then I lose my 5% discount for using my Continental credit card for an online reservation, I have to pay a $10 fee, I lose my 500 online booking bonus, and I lose 50% of my EQMs for the ticket. So I would rather not do that.

Beware when mailing in Certificates
 

Earlier this year I booked two CO flights for my wife and me --- one for Sept and the other for Nov --- using my $99 companion certificate for one flight and my wife's for the other. As per the CS's instructions, I mailed both certificates (the originals, since photocopies are not accepted as per the certificate instructions) and the Flight Confirmation info to the Houston address she gave me.

I kept checking my On-Line OP Account data month after month, not seeing anything to suggest receipt of the coupons. I probably made five or six calls to Elite OP Line --- and got the same response each time: the booking was preserved but the certificates had not been received so no confirmation for the discounts was entered. Each of the CS reps told me that they were able to see the content of my previous telephone calls --- but there was nothing they could do. I finally wrote a letter (using gentle tones, not an angry assault on CO) to the OP Service Center expressing my frustration, and I included photocopies which I had originally saved for my own records. Finally, someone at CO OP took pity on me and actually called my cell phone to tell me it had all been straightened out --- and indeed it was.

Lessons learned: (1) either do not ever use coupons/certificates with CO or make lots of photocopies before mailing the originals; (2) use Registered Mail with Return Receipt Requested. At least if the Return Receipt comes back to me, I will know that OP, not the USPS, lost the paperwork.

By the way, my wife and I got 100% EQM and we were upgraded with FF Miles as well on both the regular and the discounted tickets.

You're lucky and good. The same thing happened to me, and I had photocopied the certificate, as well. When the status of the reservation hadn't changed, I called them a week before the trip. They said I was out-of-luck -- even with the photocopies. Photocopies were no good. They said I should have sent the certificates via certified mail. The best they could do was offer me the opportunity to buy the tickets pre-discount.

Whenever I redeem certs via mail-in, I always have the phone rep. record the cert's promo code and serial number in the comments of the PNR - if the cert goes astray, it can still be applied to your booking with that info.