Frankly, the only reliable rebates I have participated in are from Staples. I have cashed in over 300 Staples rebates (mostly paperless Easy Rabbits) and only one was denied, and a trip to the local store cleared that up.
That said, I follow the directions to the letter, I make copies (.pdf's) of everything, and I organize the rebates in a folder and track their progress. It is a pain, but I have my method and have scored literally thousands of dollars worth of product for very, very little out of pocket costs after the rebate comes back.
Recently I fell for the RS deal where they offered a case, PS, and toolkit for a great price after rebate. They us onrebates.com which looks better in the surface than it really is (For instance you have to send physical items, UPC, receipt, etc. to get your rebate even thought you register it online) and for a price they offer these very fast turns, but they want like $3.50 a rebate for that level of service.
I have a feeling with all the troubles RS is going through now that I will take it up the but t on these latest rebates. We shall see I guess.