The number of photos you can submit depends on the format. For example, you can fit up to 400 photos on a large 20x40-inch poster for $25, or you can spend half the price on two minibooks that can hold up to 50 photos each.
The Printstagram site is vague on details and neglects to mention the print quality of the photos themselves, but I doubt anyone would even notice if the prints turned out grainy or overexposed.
Regardless, any of the projects would make a creative gift for the Instagram-obsessed. Check out other ways to have fun with Instagram photos at Printstagram.
Correction, December 5: This blog post originally had the incorrect spelling of Printstagram.