I made a purchase yesterday that stated in the description that it was sold in .psd format. When I got the product there were no individual layers and it should have been sold in .png format. You could not use it with patterned papers at all and it seriously washed out the color of any solid papers because you had to use the blending mode of overlay. I contacted the owner of the store and as yet she will not give me my money back even though the files are not usable. The store owner talked about degradation of quality to save them as a .png file. This is inaccurate. The quality changes by 1/1000th of a pixel per inch which does NOT degrade your quality at all. The store owner is saying that the reason they sell them as .psd files is because you go from 300 dpi to 299.99 dpi. In other words, you would have to have a image 1000 inches wide before you lost a single pixel!
Your tip: Beware of ANYTHING sold in .psd format! You may not get what you think you're getting! Plus, .psd is a large format so it would just take up a lot of space on your hard drive.