Siege is just another load testing software. The new thing here is that we offer load testing as an online service. No need to install, configure or maintain any special software or hardware. Test configurations and results are always accessible, on the web.

If you're interested in running your own load testing software I would recommend the Grinder - http://grinder.sourceforge.net - which is very nice and flexible. If you need to generate a lot of load, curl-loader might be of interest - http://curl-loader.sourceforge.net