I'm also a little surprised to find out about the MkII's being "flops"....
I've had my stainless 5.5" bull barrel for...hmmmm...probably about 32 or 33 years now... I've lost count of the number of bricks I've shot through it...
It's starting to limber up pretty nicely...
The only issue I've had is shooting "dirty" ammo in it. It does tend to get a little sluggish after a few hundred rounds of ammo, and needs to be cleaned.
Once cleaned, it runs like a top.
It's very simple to disassemble.... re-assembly is only a touch tricky, until you learn the simple technique... then it's about a 20 second job.
It prefers Mini-Mags, or equivalent... copperwashed quality ammo. I have shot standard velocity stuff with good results, and only occasional mis-feeds. With the quality stuff, it's pretty much flawless..... unless I let it get too dirty.
I also have a Buckmark that is a very nice pistol, as well. I had to replace the little buffer in the slide recently, but it had never been dismantled before. It has not been shot a lot (yet).... mostly sat in a closet, but I plan to "exercise" it pretty regularly.