It's obvious that every time tracker is simple - no one would say it's sophisticated.
I also use a simple one
It's called OnePageOnly -
http://onepageonly.net/ .
It's an online application, so you don't have to install anything.
But what I like most about it, is the fact that it is accessible. So I can start my work on PC, laptop, anything and then continue my work while travelling by bus or train on my phone.