I actually bought one and made a video of me using it for YouTube. It was part of a trial program that requested I do all that. Hope it helps you make a decision.
I also found a place to buy it for a lot cheaper than 170. In fact about half that cost, so if it is something you want check it out on my site.
The main thing it does not do, that some complain about, is that it doesn't clear the codes on your cars computer. But if you want a mechanic to fix it that is the last thing you want to do because they wouldn't know whats wrong!
Anyways, here's the links to both of them. Don't laugh it was my first YouTube video! =)
my review is at best-reviews(dot)org
my youtube is at youtube(dot)com/watch?v=vWLEj9icXoI