I hate to be less than truly helpful, but... I have one, I just haven't used it since I installed it. One problem is, if you ever take it to a mechanic & he has to drain the oil (for, say, doing a new rear main seal), he'll be a little confused at first by the weird plug, but once he figures out you just need a big wrench he'll take it out that way... but you have to warn him or he might throw it away & replace it with an OEM plug & that would suck.
As for whether it prevents sludge from draining: if you're worried about it, you can always remove it completely once every, oh, 3-4 oil changes to be more thorough (occasionally). Admittedly, it defeats the purpose of having the QD, but peace of mind is invaluable, so I intend periodically to do the old fashioned oil change.