"Packet Shapers"

I was wondering if anybody out there has had any experience with "Packet
Shapers," which claim to be able to limit traffic to a particular host,
host+port, or host+port+url without dropping packets. They apparently watch
traffic flows and keep track of connections, then dink around with TCP
window size information to slow traffic down if needed.

The one we have been looking at is called "The Packeteer"
(http://www.packeteer.com), but I have seen a few others (one of which had a
really good picture of a pig in the ad).

Do these things work as advertised? Is anybody actively using them inside
their networks? I don't know enough down-and-dirty information about TCP to
know if this should work, or if it's just a plastic shell filled with

Thanks for any information. Email if you like, I will post a summary if
people are interested.