As the topic suggests, I've had my MM QK now for 3 months. Overall, I am very happy with this device and glad that I chose it. It's very comfortable, and as such, I wear it continuously; maybe take it off every couple of weeks to make sure all is well, and shave the (few, small) areas that I can't shave while I'm wearing it.
If you're thinking of ordering one, I strongly suggest going with a cheaper plastic model first (I recommend the CB-6000(s) line) to get a rough idea of (base ring) size and whether or not you really want to wear something long term. Also highly recommend the sizing rings sold by MM to confirm what you think is the right size based on wearing the plastic device.
Back to the QK - I've already said it's comfortable. It's easily concealable under blue jeans, trousers, shorts, etc. It is not concealable under running tights or the like; however I did go to spinning class last friday wearing it under padded bike shorts. I don't think it was noticable to anyone other than myself - my wife said she couldn't tell unless she looked close (which no one is likely to do).
I ordered my QK with the security screw option, and haven't had any issues with it, other than losing a screw while on vacation (I dropped it and it rolled out of sight). Luckily, at the time, I had the spare screw along, so was an easy 'fix'. No joy finding a replacement screw locally though
Would hate to have to bother MM to send me a few extra screws, but might have to.
Anyway, not much else to say as I certainly have no complaints. Well, I guess I have a minor one, although I'm sure that if I sent it back to MM, they would be able to modify it; so maybe more of an observation than a complaint. For me, it's not a big deal, so I haven't sent it back. Anyway, for me, I am not really able to urinate standing up - seems like the two items that need to line up aren't usually lined up (you know what I'm talking about). One of the horizontal bars is usually in the way. Anyway, as such, it can be challenging using a urinal (I tend to avoid it). But as I've said, for me it's not a big deal as I generally prefer sitting down for that performance.