I'm another one who really enjoys alone time. I have no problem going to the movies or dining out alone. I prefer to shop alone, because I find it so boring to stand around while other people browse. I enjoy my alone time at home as well, since it makes it so easy to curl up and get lost in a good book.
The only thing I really have no desire to do alone is go on vacation. I enjoy company on vacations (but not too many people). I love sharing vacations with DH and couldn't imagine going on one without him. I often go through the single rider line at WDW without DH, and that's just fine, but I don't think I could do an entire Disney trip solo.