Overall Satisfaction with Time Doctor
I used Time Doctor for myself to record how long I spent on certain tasks. It goes very deep and has a lot of metrics to measure your work and also help you stay on task. It does have to be manually activated, though, so you can forget to activate it and do a bunch of work without recording any time. Also, its features can be overwhelming, especially if you just use it to record yourself and not an entire company's worth of time. A simplified version with a few essential measurements that are good for self-employed people would be very helpful.
RescueTime always runs automatically in the background and is integrated on the task bar (rather than being a standalone application). It also has an easier-to-navigate interface and sorts your tasks/program usage by level of productivity.
Good for businesses with multiple employees, somewhat cumbersome for individuals.