I haven't seen reports on this lately, so I thought I'd share my own experience.

In mid September I bought a video card for a PC at Newegg, for about $300. I kept an eye on and off on the price, and in late October I saw it for exactly $50 cheaper. That was within the 90 day price protection period by Discover, so I called them to initiate the process.

The number you call is answered by Discover, by they transfer you to a third party vendor that manages the program. The CSR for this vendor asked me to confirm my name, email address and the last four digits of my card. She said I'd receive a link via email to file the actual claim.

The link arrived within moments, and it took me only 10 minutes to get it all done. You need to upload copies of:

Invoice showing the price paid
Screenshot showing the lower price
Screenshot showing the original charge on your card

About three weeks after that I got a check in the mail for the price difference ($50 in this case).

All told, between the call, collecting screenshots and filing online I spent maybe 15 minutes.

Not bad.