I do not own it, but I have put one in a friends car and tuned it, it works but I do not like a few things about it, you cant tune on the fly, any time the car is running, you have to disconnect the usb cable from the computer, so every time you want to change the tune you must hook the laptop back up then adjust the tune and upload it to the ecu, then remove the laptop and start the car and make your pull. It is ok if you have a relatively stock car and can use their base tune, but if you can get a base tune for something similar to what you are running, you are fucked and it is going to take some time and is very frustrating having to disconnect and reconnect the laptop all the time. With many standalones you can tune going down the road if you need to, and have a wideband, you see a lean spot and you add a little fuel and load it while the car is at the stop light, and many of them also allow you to monitor engine parameters through the software. It is also a pain in the ass to get the software setup as you have to send them a request code and wait for them to send you an activation code back, and the software is not Vista or Windows 7 ready. On my laptop I had to run the software in XP SP3 compatibility mode and still hade a few issues.
Here is the megasquirt interface which is much easier to use and costs around the same ammount



here is a demo of the software
http://www.youtube.com/watch?v=FHMWjhRinBoAnother thing with the megasquirt is the hud which can be purchased separately
http://www.diyautotune.com/catalog/lcdash-digital-touchscreen-dash-display-for-megasquirt-p-167.html