This is a good idea for people to post their redemption experiences. Can see which booking classes need to be available and which airlines are actually available. I believe that they have special negotiated rates with certain airlines which they may prefer to book people on.

Award type: 50k economy to Europe
Date: July 2005
Number of days redeemed in advance of trip: 14 days
Lowest prevailing price: $845 (via AA)
Airline redeemed on: AA
Prevailing price for booked flight: $845
Taxes charged by Global Impact: $129
Earned full miles: Yes

For me, I redeemed a 50k award to Europe exactly 14 days before my trip during mid-July (peak season for this route). I prefer flying on AA, so I used various price search engines to determine the prevailing price and which airlines were cheapest. I was flexible in my choice of dates, so I chose a date on which AA was coming up the cheapest.

Basically when you call, you specify your origination, your destination, and your travel dates. I was only given one flight option which was on AA. Unfortunately, I did not query other days. Using ITN/CWT, I could see the flight on the way over was wide open, but the flight on the way back had only one spot open in V class. After I booked my flight, the price on AA.com actually jumped to $1300 as I snagged the last V fare (and this flight was very full--I got op-upped to J on the way back!).

I mentioned on a different thread that I believe that GI uses AAdvantage Incentive Travel certificates for AA. The rep mentioned something about a certificate that they have with AA, and they didn't know at the time of booking how much the taxes were going to be (which certainly would not be the case if they were actually buying a ticket). Oh, and GI booked me into V class (which is also the class that these certs use). He said that the certificate they have with AA only says the taxes are between $100 and $150. Incidentally, the taxes are billed directly by GI, and on my AA ticket receipt, the taxes were paid by an Amex (presumably GI's card).

Hope this helps (and would love to see other people's experiences!).