Installed Pergo in downstairs living, family, dining, kitchen, and hall. December, 2002. Pergo Presto (snap together), no glue. Installed ourselves (the homeowners). Allowed 1/4 inch breathing space all the way around. No problem yet with "curling", or planks losing shape (it has only been a few months, though). But install took A LOT longer than we thought. LOTS of cutting. And Pergo is NOT scratch-resistant AT ALL, and NOTHING will get the scratches out. To keep floor looking good you must have absolutely no abrasive traffic. Appearance is okay, but Pergo is NOT scratch-resistant to even the tiniest disturbance. Many regrets.