So far so good, it is aimed at developers (I think) and has the advantage of giving you the option to change 'engine' without leaving the current web page. In laymans terms it means you can view a website in Internet Explorer, Firefox, Chrome or Safari emulation without opening/closing browsers.
Could be very useful if we get more of the problems we've had recently.
I'm not suggesting that we all change to it but anyone who is interested in the more technical side of the interweb ;) might find it worth a look.
Gecko engine = Firefox Trident = Internet Explorer Webkit = Chrome/Safari