On my itunes there is a playlist called LimeWire. All tunes downloaded from LW go automatically into that playlist, and stay there until I am happy with them and I clear them. My way means that I might share a bad file for a day or so, but no more than that. The playlist is an ordinary one (not a smart one) and if I delete it it reappears. Once in a while a song will not import to iTunes and then I have to manually find it and open it from the iTunes folder (iTunes is set as my default mp3 player). I then have to remember to copy it to the LimeWire playlist in iTunes.
I dappled with one or two of the Betas recently and this behaviour remained unchanged ... I think anyway...
normally I use LW 4.8.1. iTunes 4.9 Mac OSX 10.3.9
My iTunes music folder is the same as my Save Directory, but I only share selected folders from this as well as from other places. iTunes importing is enabled in Limewire.
Without this Limewire playlist I would find it very hard to keep track of things, I thought everyone had it, but it might depend on all the conditions I have mentioned.
BTW There seems to be a new default setting to put all downloads straight back into share, whether they are destined for a shared folder or not. No doubt you have dissabled that option!
I know this was not quite what you were looking for, but it seems like we both want to know what we are doing, (unlike a lot of folks who share all their preview files and god knows what else!) and this works for me.