Avoid Marvin Integrity and possibly the Company
I just bought a house full of Marvin Integrity (fiberglass) windows and they are horrible. The doors barely roll and the sliders bind and drag through the entire travel. The sales rep tried one window that my wife can barely move and he said it was "normal" and told me that these are a "low-end" window, but certainly not a low-end price. Marvin is apparently willing shovel manure and call it service. Avoid these windows and probably the entire Company.