I wanted to share my recent experience to stop anybody from making the same mistakes I did. We found a fabulous diamond at Blue Nile for 1/3 less than a local jeweler would charge - $18k vs $27k. I decided to triple-dip on the miles/points by a)using my Starwood card, b) buying gift certs via links to giftcertificates.com, and c) redeeming the GCs at blue nile via Marriott rewards link.

The first problem was the credit limit on the Amex. We asked for an increase but because we asked for >$25000 it had to go through a review so it took 3 days. So keep that in mind if you have a specific card you want to use - ask for your credit limit increase before you find a diamond/ring that you must have today.

It got worse when I started dealing with giftcertificates.com. I was willing to deal with the $250 max, but I also had to deal with a $2499 per order max for earning points on the GCs. After placing 6 orders for a total of $13700 I decided that was enough (it was a total of 56 $250 and $100 GCs) and that I would pay the rest to Blue Nile directly with the *wood Amex. GC.com immediately put all my orders on hold for "review" but meanwhile, a hold for $13700 had been placed on my Amex. After multiple phone calls & e-mails to both GC.com and Amex over 3 days to get the order approved I was finally told this morning that it was approved. Then an hour later I was called by gc.com to say they just weren't comfortable with an order that size, despite the authorization from Amex, and they would cancel my order and release the hold on my card.

So I finally got to order my diamond today after about 10 days of dealing with Amex and then GC.com. I got fewer points than I wanted, but still quite a few - 50k Marriott Rewards points and >18,000 *wood points. It is on its way and will be here Monday!