Well, this was quite unexpected and something worth passing along. The window that broke was 8-9 years old, we didn't install it, we don't have the receipt for it, but with one brief call to the company about the window, they are sending us out a totally new sash. Normally they would have me get it through where they were bought, since that's where the windows were purchased and they handle the warranty service on the windows they sell, but since this is an older discontinued model they're sending it to me directly.
Now, as long as it doesn't turn out to be a PITA to install (which I can't imagine it will be), I will call this a good experience and excellent customer service. I've always said that it's not about someone never making mistakes (or never having a product fail), it's how you respond when a mistake is made.