But there is one issue that I felt they neglected to mention in their article. The windows have argon gas inside to provide insulation and while the argon gas may eventually leak out and ruin the insulating properties of the glass, I'll guarantee that you'll notice a cool draft in your condo long before the glass fails.
That's because of the frame. From what I've seen, its not uncommon for the window to be seated in a metal frame that extends on both sides of the glass. This means that when the temperatures drop, the metal frame itself will be a conduit for heat to flow from your apartment. Doesn't matter how good the insulation of the windows is.
Something to consider if you're looking at buying a condo.