Seems to me there are many personal preferences but no such thing as a "bad" ruger MK.
A guy at work became a pretty good friend of mine and a range buddy when I discovered that he owned a handgun and was a bit of a shooter. But a couple years ago when he owned only one handgun, he was looking to expand his world to others.
I very heavily suggested that he needed a rimfire handgun. I told him that one of the ones I had was likely the finest firearm I owned...on the simple basis of how well it's worked for how long, it's function, accuracy, build quality, and pure enjoyment I get from it. My KMK-512, a stainless, 5 1/2" bull barrel Mark II target.
It made sense to him that a rimfire was a great idea. So much trigger time for a low investment cost and ammo for a fraction of the cost of center fire. His primary gun was a 1911 and he's got small hands, so the idea of the 22/45 seemed to make the most sense to him.
I suggested he put real effort in to finding a clean, used Mark II, for reasons I've already stated. Instead, he bought a brand new, box fresh 22/45 Mark III.
He's struggled through over two THOUSAND rounds and neither one of us has -EVER- seen the pistol make it through a 10 round magazine. He's tried no less than six different brands of ammo. It stops in many ways, but it's favorite failure is a simple stove pipe. You can set your watch by this pistol -- it will not fire 10 rounds without a stoppage.
He hasn't yet contacted Ruger. I've bugged him about it. He will eventually, I'd imagine. In the mean time, he bought a GSG 1911-22 and put well over 2,000 rounds through that pistol and when run with 36gr bulk plated Federal Champion (the Wal-Mart special), it gives a failure rate of less than one per bulk box. My GSG is the same way...I don't even get 1 failure in 525, mine does even better.
I've got more than a half dozen rimfire semi-auto pistols and though my GSG is one thoroughly amazing handgun...I simply don't own a firearm that's as, well, perfect
as my KMK-512, Mark II.
His brand new, straight out of the box 22/45 Mark III is the textbook definition of a lemon.
I have very little doubt that a trip to Ruger (which would likely be an ultra-fast turn-around) would have that pistol running up to Ruger standards. However... that pistol and my pistol are light years apart.
It's absolutely a "bad" Ruger MK.