First, I was able to get a bunch of stuff done. It's amazing how much you can get done when there's no one expecting or wanting you to be somewhere at a specific time, and meals are whenever you feel like eating. In the first few hours I was able to accomplish about a half dozen errands. I went to several stores that I had gift cards to, and I was able to take time and browse and see what I wanted to get, something that I don't normally have much time to do.
Second, I realized how quiet it was. The dogs were very subdued, without the kids around, and they weren't really barking at all. There was no one else in the house. No one talking, no one playing, no one arguing, no one laughing, no one singing. It was very quiet.
As an introvert, I don't mind being by myself. In fact, I enjoy it. Being by myself is what recharges my batteries, and there are aspects of being alone that I really like. However, it was very quiet.