I'll keep this short:
When I built a new babylon5 recently, the first video card I ordered was a Gigabyte card which was priced with a $20 mail-in rebate (outsourced to 4myrebate.com, by the way). I filled in all the rebate paperwork and sent it in. The rebate was declined because they claimed the included paperwork did not show the item purchased or the purchase date.¹ (I'd highlighted the item on the invoice with yellow highlighter.) I forwarded them a copy of the NewEgg email invoice. They refused to accept it. I emailed them a PDF of the invoice. They refused to accept it and said they couldn't open email attachments for security reasons. I printed a new copy of the invoice directly from NewEgg.com and mailed it to them along with their resubmission form. They have not acknowledged receipt.
At this point there is no doubt in my mind that GigaByte (or at least, 4myrebate.com) never for a moment intended to honor the rebate.
Oh, the video card? It failed (stopped outputting video on its DVI port) after two weeks. I couldn't get it replaced by NewEgg because I was required to cut the UPC code out of the box to get the rebate. I still don't have an RMA authorization from GigaByte.
Needless to say, I won't be buying any more GigaByte products. I advise others to follow suit.
 I eventually learned, by the way, that all they filed was the rebate form (with attached UPC barcode from the box, as stipulated) and the page showing the item purchased (that's right, the "item purchased" data which they said they didn't have; it was right there in black and white). They apparently threw away the first page of the invoice,with the purchase date on it, without bothering to scan it in.