The best thing here is that you can't cheat it. This program says truth and only truth about what I am doing in front of my computer and it was surprisingly powerful experience as finally I was able to see in real numbers how much time am I wasting using social media or other things during the time I should work. It was much easier to get more productive simply by setting up a goal to have productivity pulse over 75% every week. It's a great motivator.
I don't really like design and interface - colors seems to be a bit muddy and not visually attractive. It's not a big deal though as this program is suppose to work in background and you see it's interface for short time only.
Interface is also not fully functional, it's hard to easly skip between categories while checking detailed time spent on them.
I also think that this program might not be that useful for people who for example do blogging, simply because Rescue Time has it's own system of qualifying sites as distracting or productive. If your job is about reading and writing blogs or something like that it would mean that you have to edit distraction level for each site to see real producitvity pulse.
I'm using free version of this program though and I'm not sure if these problems exist in premium version.