Good explanation of the Apple feature. In a nutshell: it slows down your connection in an attempt to make it more stable. Turn it on only when you need it.

Extensive bandwidth monitoring/graphing software.

Open your own damn ports!

More commands in the comments - good for checking over a machine for suspicious services.

We've only got two routers, it can't be that hard to link them together (famous last words).

For those with bandwidth caps...or are about to. :(