I don't think that using a debugger = you don't understand whats going on in your code. I've had many situations where it helped me understand a great deal what was going on. Plus, its a built in tool, so I don't have to waste time writing logging code or anything of the sort. I've also had situations where I worked with another programmer, who rarely used it, and often times got his understanding wrong when he puzzled it out. He eventually figured it out, but it was debatable whether it saved time from using a debugger.