Your part right and part wrong. QoS only applies to QoS aware applications. the wrong part is that just doing the gpedit.msc part. There is a second part to the tweak. A guy named Spooky over at wxperience originated the tweak. Go on over there and search for it under his name. He fully explains the tweak in a two part post made about two weeks before winXP went gold. Evidently he is a beta tester.
It has been discovered that on a small majority of NIC cards there does appear to be a slight boost in speed. If I remember correctly it concerns some intel and 3com cards - the high end cards - that have the fancy on board memory / processor and stuff. It seems that part of the rom on the card contains some code that is in fact QoS aware. I dont know the all in all of it, but MS also did some test results which appeared late last year on that UK news page - cant remember the name of it right now, and there was a small blurb about it on tech TV as well about a week after they debunked the QoS thing.
About 99.9% of the users out there will never see a true speed boost in their connections from this. But...there are certain parts of a default XP install that are QoS aware to a certain degree, to what degree I dont know, but this was also bought up on tech TV last year. As you can probably tell I watch a lot of the tech tv
. Anyway, the parts that are QoS aware in a little way are some of the serveices that run. So if you disable this in gpedit.msc some people see a slight apparent boost in computer operation, which in some ways helps equate to a slight connection speed boost some times because now the OS doesn't have to worry about the QoS any more. Or something like that.
I'm trying to recall all this from memory. sorry if I may have mis-directed or I may have even got some of it a little wrong, but for the most part I think a lot of its correct.