I've read the book. Basically, the features I have are the minimum I needed where I first rolled out the system (my day job). We had to have something that lets people share tasks, and keep track of time. Like they also say in the book, I realize those features aren't for everyone, so I'm happy to concentrate on the niche of people who need them. At work, they really like the system, so I'm confident they're out there.
I recommend reading the whole book Getting Real (free from 37signals) especially chapter 5 on feature selection.